Solid-state imaging device and electronic apparatus

ABSTRACT

A solid-state imaging device includes a layout in which one sharing unit includes an array of photodiodes of 2 pixels by 4×n pixels (where, n is a positive integer), respectively, in horizontal and vertical directions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/366,612, filed Dec. 1, 2016, which is a continuation of U.S. patentapplication Ser. No. 15/219,007, filed Jul. 25, 2016, now U.S. Pat. No.9,543,341, which is a continuation of U.S. patent application Ser. No.15/079,599, filed Mar. 24, 2016, now U.S. Pat. No. 9,577,006, which is acontinuation of U.S. patent application Ser. No. 14/857,535, filed Sep.17, 2015, now U.S. Pat. No. 9,357,148, which is a continuation of U.S.patent application Ser. No. 14/564,750, filed Dec. 9, 2014, now U.S.Pat. No. 9,179,082, which is a continuation of U.S. patent applicationSer. No. 14/107,839, filed Dec. 16, 2013, now U.S. Pat. No. 9,049,392,which is a division of U.S. patent application Ser. No. 13/609,596,filed Sep. 11, 2012, now U.S. Pat. No. 8,638,382, which is a division ofU.S. patent application Ser. No. 12/684,445, filed Jan. 8, 2010, nowU.S. Pat. No. 8,314,870, which claims priority to Japanese PatentApplication Serial No. JP 2009-006892, filed in the Japan Patent Officeon Jan. 15, 2009, the entire disclosures of which are herebyincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an MOS Si substrate and an electronicapparatus, such as a camera, having the solid-state imaging device.

2. Description of the Related Art

Amplification-type solid-state imaging devices represented by MOS imagesensors such as CMOS (complementary metal oxide semiconductor) imagesensors are known as one type of solid-state imaging devices. Moreover,charge transfer-type solid-state imaging devices represented by CCD(charge coupled device) image sensors are also known. These solid-stateimaging devices are broadly used in digital cameras, digital videocameras, and the like. In recent years, as solid-state imaging deviceswhich are mounted on mobile apparatuses, such as camera-incorporatedmobile phones or PDAs (personal digital assistants), the MOS imagesensors have been used more than the CCD image sensors because the CMOSimage sensors are advantageous in terms of lower power supply voltage,smaller power consumption, and the like.

An MOS solid-state imaging device has a configuration in which aplurality of pixels is arranged in a two-dimensional array, wherein eachpixel is composed of a photodiode serving as a photoelectric conversionunit and a plurality of pixel transistors. In recent years, with theminiaturization of pixels, in order to reduce the area occupied by thepixel transistors per pixel, a so-called multi-pixel sharing structureis proposed in which a part of the pixel transistors is shared by aplurality of pixels. For example, Japanese Unexamined Patent ApplicationPublication Nos. 2004/172950, 2006/054276, and 2006/157953 describe asolid-state imaging device with 2-pixel sharing structure.

SUMMARY OF THE INVENTION

However, in MOS solid-state imaging devices, it is desirable to achievea further increase in resolution by miniaturizing the pixels further.However, a further miniaturization of the pixels may lead to a reductionin the aperture area of a light receiving portion and thus sensitivitydecreases. Therefore, it is desirable to achieve improvement insensitivity even when pixels are miniaturized.

It is therefore desirable to provide a solid-state imaging devicecapable of achieving improvement in sensitivity even when pixels areminiaturized and an electronic apparatus having such a solid-stateimaging device.

According to an embodiment of the present invention, there is provided asolid-state imaging device having a layout in which one sharing unitincludes an array of photodiodes of 2 pixels by 4×n pixels (where, n isa positive integer), respectively, in horizontal and verticaldirections.

In the solid-state imaging device according to the embodiment of thepresent invention, since one sharing unit includes an array ofphotodiodes of 2 pixels by 4×n pixels (where, n is a positive integer),respectively, in horizontal and vertical directions, the number of pixeltransistors per pixel can be decreased, and thus the aperture area ofeach of the photodiodes can be increased. Moreover, since one sharingunit includes an array of photodiodes of 2 pixels by 4×n pixels,respectively, in horizontal and vertical directions, the readout wiringscan be arranged independently for each pixel, and thus pixel additioncan be performed within the floating diffusions. Furthermore, it ispossible to decrease the area of the column signal processing circuit.

According to another embodiment of the present invention, there isprovided an electronic apparatus including: a solid-state imagingdevice; an optical system that guides incident light to photodiodes ofthe solid-state imaging device; and a signal processing circuit thatprocesses output signals from the solid-state imaging device. Thesolid-state imaging device has a layout in which one sharing unitincludes an array of photodiodes of 2 pixels by 4×n pixels (where, n isa positive integer), respectively, in horizontal and verticaldirections.

Since the electronic apparatus according to the embodiment of thepresent invention includes the solid-state imaging device, the number ofpixel transistors per pixel can be decreased, and thus the aperture areaof each of the photodiodes can be increased. Moreover, since one sharingunit includes an array of photodiodes of 2 pixels by 4×n pixels,respectively, in horizontal and vertical directions, the pixel additioncan be performed within the floating diffusions, and the area of thecolumn signal processing circuit can be reduced.

According to the solid-state imaging device of the embodiment of thepresent invention, since the aperture area of the photodiode can beincreased, it is possible to achieve improvement in sensitivity evenwhen the pixels are miniaturized.

According to the electronic apparatus of the embodiment of the presentinvention, since the aperture area of the photodiode in the solid-stateimaging device can be increased, it is possible to achieve improvementin sensitivity even when the pixels are miniaturized. Therefore, it ispossible to provide a high-quality electronic apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an exemplary configuration ofa solid-state imaging device according to an embodiment of the presentinvention.

FIG. 2 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 1.

FIGS. 3A to 3C are exploded planar layout diagrams of one sharing unitaccording to Embodiment 1.

FIG. 4 is a schematic cross-sectional view of an example of a two-layerwiring structure of Embodiment 1.

FIG. 5 is an equivalent circuit diagram of one sharing unit having astructure with 8 pixels and 10 transistors in the solid-state imagingdevice according to Embodiment 1.

FIG. 6 is a layout diagram of a main part of one sharing unit in a pixelportion of a solid-state imaging device according to Embodiment 2.

FIG. 7 is a cross-sectional view used for explaining diffraction limit.

FIG. 8 is a graph used for explaining diffraction limit.

FIG. 9 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 3.

FIG. 10 is a layout diagram of a first-layer wiring of Embodiment 3.

FIG. 11 is a plan view of a main part of FIG. 9.

FIG. 12 is an explanatory diagram used for explaining Embodiment 3.

FIG. 13 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 4.

FIG. 14 is a schematic cross-sectional view illustrating an example of aphotodiode in the pixel portion of the solid-state imaging deviceaccording to Embodiment 4.

FIGS. 15A and 15B are layout diagrams of one sharing unit in a pixelportion of a solid-state imaging device according to Embodiment 5.

FIGS. 16A and 16B are layout diagrams of one sharing unit in a pixelportion of a solid-state imaging device according to Embodiment 6.

FIG. 17 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 7.

FIG. 18 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 8.

FIGS. 19A and 19B are process diagrams illustrating an example of aformation method of a dot-shaped structure of Embodiment 8.

FIGS. 20A and 20B are process diagrams illustrating another example of aformation method of a dot-shaped structure of Embodiment 8.

FIG. 21 is an explanatory diagram illustrating the function of thedot-shaped structure in Embodiment 8.

FIG. 22 is a cross-sectional view illustrating an example of a state ofa dot-shaped structure and a wiring formed by a two-layer metalstructure in Embodiment 8.

FIG. 23 is a cross-sectional view illustrating an exemplary state of adot-shaped structure and a wiring formed by a two-layer metal structurein Embodiment 8.

FIG. 24 is a cross-sectional view illustrating another exemplary stateof a dot-shaped structure and a wiring formed by a two-layer metalstructure in Embodiment 8.

FIG. 25 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 9.

FIG. 26 is a cross-sectional view of a main part of one sharing unit ina pixel portion of a solid-state imaging device according to Embodiment10.

FIG. 27 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 11.

FIG. 28 is an equivalent circuit diagram of one sharing unit having astructure with 8 pixels and 11 transistors in the solid-state imagingdevice according to Embodiment 11.

FIG. 29 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 12.

FIGS. 30A to 30C are exploded planar layout diagrams of one sharing unitaccording to Embodiment 12.

FIG. 31 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 13.

FIG. 32 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 14.

FIG. 33 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 15.

FIGS. 34A to 34C are exploded planar layout diagrams of one sharing unitaccording to Embodiment 15.

FIG. 35 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 16.

FIG. 36 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 17.

FIGS. 37A to 37C are exploded planar layout diagrams of one sharing unitaccording to Embodiment 17.

FIG. 38 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 18.

FIGS. 39A and 39B are first exploded planar layout diagrams of onesharing unit according to Embodiment 18.

FIGS. 40A and 40B are second exploded planar layout diagrams of onesharing unit according to Embodiment 18.

FIG. 41 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 19.

FIGS. 42A and 42B are first exploded planar layout diagrams of onesharing unit according to Embodiment 19.

FIGS. 43A and 43B are second exploded planar layout diagrams of onesharing unit according to Embodiment 19.

FIG. 44 is a third exploded planar layout diagram of one sharing unitaccording to Embodiment 19.

FIG. 45 is a layout diagram of one sharing unit in a pixel portion of asolid-state imaging device according to Embodiment 20.

FIGS. 46A and 46B are first exploded planar layout diagrams of onesharing unit according to Embodiment 20.

FIGS. 47C and 47D are second exploded planar layout diagrams of onesharing unit according to Embodiment 20.

FIG. 48 is a plan view illustrating a schematic layout of a solid-stateimaging device according to the embodiment of the present invention.

FIG. 49 is a layout diagram used for explaining the advantages of theembodiment of the present invention.

FIG. 50 is a layout diagram of a reference example used for comparisonwith the advantages of the embodiment of the present invention.

FIG. 51 is a layout diagram illustrating Modification 1 of anamplification transistor in the solid-state imaging device according tothe embodiment of the present invention.

FIG. 52 is a layout diagram illustrating Modification 2 of anamplification transistor in the solid-state imaging device according tothe embodiment of the present invention.

FIG. 53 is a layout diagram illustrating Modification 3 of anamplification transistor in the solid-state imaging device according tothe embodiment of the present invention.

FIG. 54 is a layout diagram illustrating Modification 4 of anamplification transistor in the solid-state imaging device according tothe embodiment of the present invention.

FIG. 55 is a layout diagram illustrating Modification 5 of anamplification transistor in the solid-state imaging device according tothe embodiment of the present invention.

FIG. 56 is a layout diagram illustrating Modification 6 of anamplification transistor in the solid-state imaging device according tothe embodiment of the present invention.

FIG. 57 is a layout diagram illustrating Modification 7 of anamplification transistor in the solid-state imaging device according tothe embodiment of the present invention.

FIG. 58 is a layout diagram illustrating Modification 1 of a resettransistor in the solid-state imaging device according to the embodimentof the present invention.

FIG. 59 is a layout diagram illustrating Modification 2 of a resettransistor in the solid-state imaging device according to the embodimentof the present invention.

FIG. 60 is a diagram illustrating a schematic configuration of anelectronic apparatus according to an embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

With reference to FIG. 1, an example of a schematic configuration of asolid-state imaging device, i.e., an MOS solid-state imaging device,according to an embodiment of the present invention is illustrated. Thesolid-state imaging device 1 of this example includes a pixel portion(namely, an imaging region) 3 and a peripheral circuit portion which areprovided on a semiconductor substrate 11 (e.g., a silicon substrate).The pixel portion 3 includes pixels 2 which include a plurality ofphotodiodes serving as photoelectric conversion units and which areregularly arranged in a two-dimensional array. Each pixel 2 includes aphotodiode and a plurality of pixel transistors (namely, MOStransistors). The plurality of pixel transistors may be composed of thethree transistors, a transfer transistor, a reset transistor, and anamplification transistor, for example. In addition to these transistors,the pixel transistors may be composed of four transistors by adding aselect transistor.

The peripheral circuit portion includes a vertical driving circuit 4,column signal processing circuits 5, a horizontal driving circuit 6, anoutput circuit 7, a control circuit 8, and the like.

The control circuit 8 generates clock signals or control signals servingas the reference signals of the operations of the vertical drivingcircuit 4, the column signal processing circuits 5, the horizontaldriving circuit 6, and the like in accordance with a verticalsynchronization signal, a horizontal synchronization signal, and amaster clock. The control circuit 8 inputs these signals to the verticaldriving circuit 4, the column signal processing circuits 5, thehorizontal driving circuit 6, and the like.

The vertical driving circuit 4 is configured by a shift register, forexample. The vertical driving circuit 4 selectively scans each pixel 2of the pixel portion 3 sequentially in a vertical direction in units ofrows and supplies a pixel signal to a column signal processing circuit 5via a vertical signal line 9. The pixel signal is based on signalcharges generated corresponding to the amount of light received, forexample, by the photodiode serving as a photoelectric conversion elementof each pixel 2.

The column signal processing circuits 5 are provided, for example, foreach column of the pixels 2 and perform signal processing such as noiseremoval for each pixel column on signals output from pixels 2 of one rowusing a signal from a black reference pixel (which is formed around aneffective pixel region). Specifically, the column signal processingcircuits 5 perform signal processing such as CDS for removing fixedpattern noise inherent to the pixels 2 or signal amplification. Ahorizontal select switch (not illustrated) is connected between anoutput terminal of each of the column signal processing circuits 5 and ahorizontal signal line 10.

The horizontal driving circuit 6 is configured by a shift register, forexample, and sequentially selects each of the column signal processingcircuits 5 by sequentially outputting horizontal scanning pulses andoutputs the pixel signals from each of the column signal processingcircuits 5 to the horizontal signal line 10.

The output circuit 7 performs signal processing on signals which aresequentially supplied from each of the column signal processing circuits5 via the horizontal signal line 10 and outputs the processed signals.

When the above-described solid-state imaging device 1 is applied to afront-illuminated solid-state imaging device, a plurality of wiringlayers including a plurality of layers of wiring is formed above thepixel portion 3 and the peripheral circuit portion via an interlayerinsulating film. In the pixel portion 3, an on-chip color filter isformed on the plurality of wiring layers via a planarization film, andan on-chip microlens is formed thereon.

When the solid-state imaging device 1 is applied to a back-illuminatedsolid-state imaging device, the plurality of wiring layers is not formedon a back surface on the side of a light incidence surface (namely, alight receiving surface). Instead of this, the plurality of wiringlayers is formed on a front surface side opposite to the light receivingsurface.

The solid-state imaging device according to the embodiment of thepresent invention has an optimized feature in the layout of the pixelportion 3 when the pixels are miniaturized.

Embodiment 1: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 2, a solid-state imaging device, namely an MOSsolid-state imaging device, according to Embodiment 1 of the presentinvention is illustrated. FIG. 2 illustrates a main part of a layout ofa pixel portion. FIGS. 3A to 3C and FIGS. 4 and 5 are exploded planarviews for understanding the patterns of first-layer wirings andsecond-layer wirings. In the following description, a lengthwise orlongitudinal direction corresponds to a vertical direction of a pixelportion, and a widthwise or transverse direction corresponds to ahorizontal direction of a pixel portion. That is to say, a directionparallel to the vertical signal line is the vertical direction, and adirection vertical to this direction is the horizontal direction.

As illustrated in FIG. 2, a solid-state imaging device 101 according toEmbodiment 1 includes a pixel portion 3 in which sharing units 21 arearranged in a two-dimensional array, wherein one sharing unit 21includes photodiodes PD (PD1 to PD8) of 8 pixels in total (2 pixels by 4pixels, respectively, in horizontal and vertical directions). That is tosay, one sharing unit 21 is laid out in a so-called 8-pixel sharingstructure with 2 pixels by 4 pixels, respectively, in horizontal andvertical directions, in which two structural groups are arrangedvertically, wherein one structural group has one floating diffusion FDwhich are shared by four photodiodes PD in total (2 by 2 photodiodes,respectively, in horizontal and vertical directions). In the figure, Prepresents a pixel pitch.

One sharing unit 21 is composed of eight photodiodes and ten pixeltransistors; that is, one sharing unit 21 includes 1.25 pixeltransistors per pixel. In this example, the ten pixel transistors arespecifically broken down into eight transfer transistors Tr1 (Tr11 toTr18), one reset transistor Tr2, and one amplification transistor Tr3.

The layout in one sharing unit 21 includes a first structural portion23, a second structural portion 25, readout transistors Tr11 to Tr18, anamplification transistor Tr3, and a reset transistor Tr2. Moreover, thislayout also includes eight readout wirings 26 (261 to 268), a resetwiring 27, and a connection wiring 28. The amplification transistor Tr3includes a source region 31S, a drain region 31D, and an amplificationgate electrode 32. The reset transistor Tr2 includes a source region33S, a drain region 33D, and a reset gate electrode 34.

The first structural portion 23 includes four photodiodes PD1, PD2, PD3,and PD4, and four readout gate electrodes 221 to 224 and one firstfloating diffusion FD1 which are respectively provided so as tocorrespond to the four photodiodes PD1 to PD4 (see FIG. 3A). Thephotodiodes PD1 to PD4, the first floating diffusion FD1, and thereadout gate electrodes 221 to 224 form readout transistors Tr11 toTr14, respectively.

The first structural portion 23 on the upper side includes the fourphotodiodes PD1 to PD4 which are approximately square in shape and arearranged in two vertical and two horizontal rows with a predeterminedspacing therebetween (e.g., equal vertical and horizontal spacing). Onefirst floating diffusion FD1 is formed at the central region which issurrounded by the four photodiodes PD1 to PD4. The corresponding readoutgate electrodes 221 to 224 are formed at opposing corner portions of thefour photodiodes PD1 to PD4 so as to contact the first floatingdiffusion FD1. Each of the readout gate electrodes 221 to 224 isapproximately triangular or trapezoidal in shape with a partiallyprotruding portion 24, wherein a bottom side thereof is positioned closeto the corresponding photodiode PD and an apex side thereof ispositioned close to the first floating diffusion FD1. More specifically,the four readout gate electrodes 221 to 224 are identical in shape andare arranged symmetrically.

The second structural portion 25 includes four photodiodes PD5, PD6,PD7, and PD8, and four readout gate electrodes 225 to 228 and one secondfloating diffusion FD2 which are respectively provided so as tocorrespond to the four photodiodes PD5 to PD8 (see FIG. 3A). Thephotodiodes PD5 to PD8, the second floating diffusion FD2, and thereadout gate electrodes 225 to 228 form readout transistors Tr15 toTr18, respectively.

Similarly to the first structural portion 23 on the upper side, thesecond structural portion 25 on the lower side includes the fourphotodiodes PD5 to PD8 which are approximately square in shape and arearranged in two vertical and two horizontal rows with a predeterminedspacing therebetween (e.g., equal vertical and horizontal spacing). Onesecond floating diffusion FD2 is formed at the central region which issurrounded by the four photodiodes PD5 to PD8. The corresponding readoutgate electrodes 225 to 228 are formed at opposing corner portions of thefour photodiodes PD5 to PD8 so as to contact the second floatingdiffusion FD2. The readout gate electrodes 225 to 228 have the sameshape as the above-described readout gate electrodes 221 to 224.Therefore, the readout gate electrodes 225 to 228 are arrangedsymmetrically so that bottom sides thereof are positioned close to thecorresponding photodiodes PD and apex sides thereof are positioned closeto the second floating diffusion FD2.

The eight readout wirings 261 to 268 are connected to the readout gateelectrodes 221 to 228 of the readout transistors Tr11 to Tr18,respectively and are independently controlled by independent readoutpulses applied thereto. The reset wiring 27 is connected to the resetgate electrode 34 of the reset transistor Tr2 and is supplied with areset pulse. The connection wiring 28 is connected to the first floatingdiffusion FD1, the second floating diffusion FD2, the amplification gateelectrode 32 of the amplification transistor Tr3, and the source region33S of the reset transistor Tr2.

Furthermore, the sharing unit 21 includes a power supply wiring 29connected to the drain region 33D of the reset transistor Tr2, avertical signal line 35 connected to the source region 31S of theamplification transistor Tr3, and a power supply wiring 36 connected tothe drain region 31D of the amplification transistor Tr3.

The amplification transistor Tr3 is formed between the upper firststructural portion 23 and the lower second structural portion 25. Theamplification transistor Tr3 includes an amplification gate electrode32, which has a large gate length in the transverse direction, and asource region 31S and a drain region 31D which are formed at both endsof the amplification gate electrode 32. The length in the gate lengthdirection of the amplification gate electrode 32 is formed so as to belarger than a pixel pitch P1. In this example, the length of theamplification gate electrode 32 corresponds to a length of the twohorizontal photodiodes PD1 and PD2, namely a dimension close to twopixel pitches.

The reset transistor Tr2 is formed at the center of an upper portion ofthe upper first structural portion 23. Specifically, the resettransistor Tr2 includes the reset gate electrode 34, which is formed ina corresponding region disposed between the two horizontal photodiodesPD1 and PD2, and the drain region 33D and the source region 33S whichare formed so as to sandwich the reset gate electrode 34.

In this embodiment, the readout wirings 261 to 268, the reset wiring 27,the power supply wiring 29 that is connected to the drain region 33D ofthe reset transistor Tr2 are formed by first-layer wirings of the wiringwith a two-layer structure (hereinafter referred to as a two-layerwiring structure). The two-layer wiring structure is formed by metalwirings M1 and M2 as illustrated in FIG. 4. The first-layer wirings,that is, the respective wirings 261 to 268, 27, and 29 formed by thefirst-layer metal wirings M1 are wired in the transverse direction (seeFIG. 3B).

As illustrated in FIG. 4, the metal wirings M1 and M2 are formed via aninterlayer insulating film 39 on a semiconductor substrate 38 on whichthe photodiodes PD and the pixel transistors Tr1 to Tr3 are formed.Reference numeral 40 designates a planarization film. The metal wiringsM1 and M2 are formed by a Cu wiring of which the lower and side surfacesare covered with a barrier metal 41. An SiC film 42 is formed on thesurface of the Cu-based metal wirings M1 and M2 so as to preventdiffusion of Cu.

The four readout wirings 261 to 264 on the first structural portion 23are arranged in a corresponding region disposed between two verticalrows of the photodiodes PD. The upper two readout wirings 261 and 262are partially bent following the readout gate electrodes 221 and 222 andare arranged in parallel to each other to be connected to thecorresponding readout gate electrodes 221 and 222. The lower two readoutwirings 263 and 264 are partially bent following the readout gateelectrodes 223 and 224 and are arranged in parallel to each other to beconnected to the corresponding readout gate electrodes 223 and 224. Theupper two readout wirings 261 and 262 connected to the readout gateelectrodes 221 and 222 and the lower two readout wirings 263 and 264connected to the readout gate electrodes 223 and 224 are formed in asymmetrical layout.

The four readout wirings 265 to 268 on the second structural portion 25are arranged in the same manner. That is to say, the readout wirings 265to 268 are arranged in a corresponding region disposed between twovertical rows of the photodiodes PD. The upper two readout wirings 265and 266 are partially bent following the readout gate electrodes 225 and226 and are arranged in parallel to each other to be connected to thecorresponding readout gate electrodes 225 and 226. The lower two readoutwirings 267 and 268 are partially bent following the readout gateelectrodes 227 and 228 and are arranged in parallel to each other to beconnected to the corresponding readout gate electrodes 227 and 228. Theupper two readout wirings 265 and 266 connected to the readout gateelectrodes 225 and 226 and the lower two readout wirings 267 and 268connected to the readout gate electrodes 227 and 228 are formed in asymmetrical layout.

The upper and lower, first and second floating diffusions FD1 and FD2,the amplification gate electrode 32, and the source region 33S of thereset transistor Tr2 are connected by a connection wiring 28. Theconnection wiring 28, the vertical signal line 35 that is connected tothe source region 31S of the amplification transistor Tr3, and the powersupply wiring 36 that is connected to the drain region 31D of theamplification transistor Tr3 are formed by second-layer wirings of thetwo-layer wiring structure. The second-layer wirings, that is, theconnection wiring 28, the vertical signal line 35, and the power supplywiring 36, which are formed by the second-layer metal wiring M2, arewired in the longitudinal direction (see FIG. 3C).

The four rows of the readout wirings 261 to 264 and the four rows of thereadout wirings 265 to 268 which are respectively wired in thetransverse direction are arranged at an interwiring spacing which is setto be equal to or smaller than a diffraction limit. Therefore, theregion of the four rows of the readout wirings 261 to 264 (and thereadout wirings 265 to 268) serves as a light shielding region wherelight does not substantially pass therethrough. In FIG. 2, referencenumeral 30 designates a contact portion. In the contact portion 30,interconnections are achieved via a conductive plug that passes throughthe interlayer insulating film. In this case, a structure in which thefirst-layer metal wirings M1 and the second-layer metal wirings M2 aredirectly connected to target connection regions via the conductive plug,respectively, or a structure in which the second-layer metal wirings M2are connected to a target connection region via the conductive plug andthe first-layer metal wirings M1 is employed.

An element separation region 20 is formed between the photodiodes PD1 toPD8, the amplification transistor Tr3, and the reset transistor Tr2.Although not illustrated in the figure, as this element separationregion 20, a flat insulating film is formed in an impurity diffusionregion so as to be approximately even with a gate insulating film on theentire surface of the impurity diffusion region, for example. Theimpurity diffusion region may be a p-type semiconductor region, forexample. In this case, an n-channel pixel transistor is used as thepixel transistor, and electrons are used as signal charges.

With reference to FIGS. 3A to 3C, exploded planar views of one sharingunit 21 are illustrated. In FIG. 3A, the layout of the photodiodes PD1to PD8, the first and second floating diffusions FD1 and FD2, thereadout gate electrodes 221 to 228, the readout transistor Tr1, thereset transistor Tr2, and the amplification transistor Tr3 isillustrated. In FIG. 3B, the layout of the readout wirings 261 to 268,the reset wiring 27, and the power supply wiring 29 which are wired inthe transverse direction by the first-layer metal wirings M1 isillustrated. In FIG. 3C, the layout of the connection wiring 28, thevertical signal line 35, and the power supply wiring 36 which are wiredin the longitudinal direction by the second-layer metal wirings M2 isillustrated.

The connection between the wirings formed by the second-layer metalwirings M2 and the pixel transistor is achieved by the connection whichextends from the wirings formed by the second-layer metal wirings M2 viaconnection portions of the first-layer metal wirings M1 to predeterminedportions of the pixel transistor.

The wiring that is disposed on the peripheral circuit portion via theinterlayer insulating film is wired in two or more layers. When thenumber of wiring layers is different from the pixel portion to theperipheral circuit portion, the insulating film on the top-layer wiringin the pixel portion is formed to be thicker than the insulating film onthe top-layer wiring in the peripheral circuit portion.

With reference to FIG. 5, an equivalent circuit of the structure witheight pixels and ten transistors related to one sharing unit 21 ofEmbodiment 1 is illustrated. In this circuit configuration, the fourphotodiodes PD (PD11, PD12, PD13, and PD14) of the first structuralportion are connected to the sources of the four readout transistorsTr11, Tr12, Tr13, and Tr14, respectively. The drains of the readouttransistors Tr11 to Tr14 are connected to the source of the resettransistor Tr2. The four photodiodes PD (PD15, PD16, PD17, and PD18) ofthe second structural portion are connected to the sources of the fourreadout transistors Tr15, Tr16, Tr17, and Tr18, respectively. The drainsof the readout transistors Tr15 to Tr18 are connected to the sources ofthe reset transistors Tr2. The first floating diffusion FD1 between thereadout transistors Tr11 to Tr14 and the reset transistor Tr2 isconnected to the amplification gate of the amplification transistor Tr3via the connection wiring 28. The second floating diffusion FD2 betweenthe readout transistors Tr15 to Tr18 and the reset transistor Tr2 isconnected to the amplification gate of the amplification transistor Tr3via the connection wiring 28. The source of the amplification transistorTr3 is connected to the vertical signal line 35, and the drain of theamplification transistor Tr3 is connected to the power supply wiring 36.The drain of the reset transistor Tr2 is connected to the power supplywiring 29, and the gate of the reset transistor Tr2 is connected to thereset wiring 27 to which the reset pulse is applied. The readout gatesof the readout transistors Tr11 to Tr18 are connected to the readoutwirings 261 to 268 to which independent row-readout pulses are applied.

The color filters of the four pixels of each of the first structuralportion 23 and the second structural portion 25 may be arranged in theBayer arrangement using the primary colors red, green, and blue (RGB).Alternatively, as the color filter arrangement, various color filterarrangements can be used, such as a color filter arrangement using whiteW in addition to the primary colors red, green, and blue (RGB) or acolor filter arrangement using other complementary colors or acombination of complementary colors and primary colors.

According to the solid-state imaging device of Embodiment 1, since onesharing unit 21 has a structure with eight pixels and ten transistors,the number of pixel transistors per pixel can be decreased, andaccordingly, the aperture area of each of the photodiodes PD1 to PD8 canbe increased. Moreover, the wirings are formed in only a two-layerwiring structure, the first-layer metal wirings M1 are used for thewirings in the transverse direction, and the second-layer metal wiringsM2 are used for the wirings in the longitudinal direction, whereby theaperture area of the photodiode is defined by the vertical andhorizontal wirings. This wiring layout is not complex and does notinterfere with the aperture of the photodiode. As described above, sincethe aperture area of the photodiode can be increased, it is possible toimprove the sensitivity even when the pixels are miniaturized.Therefore, a solid-state imaging device with high sensitivity and highresolution can be obtained.

The connection wiring 28 which is wired in two wiring layers and isconnected to the floating diffusions FD1 and FD2 is formed by thesecond-layer metal wirings M2 which is distant from the semiconductorsubstrate. Moreover, the connection wiring 28 and the first-layer metalwirings M1 intersecting the connection wiring 28 meet only at itsintersections with the small-width readout wirings 261 to 268. Thefloating capacitance between the connection wiring 28 and thesemiconductor substrate and the floating capacitance between theconnection wiring 28 and the readout wirings 261 to 268 are small.Therefore, the floating capacitance connected to the floating diffusionsFD1 and FD2 is small, and thus conversion efficiency thereof does notfall even when the pixels are miniaturized. Thus, it is possible toachieve improvement in sensitivity.

In this embodiment, the wirings are formed in a two-layer wiringstructure. The wirings of the two-layer wiring structure are formed atpositions closer to the photodiodes than the wirings of a four-layerwiring structure. Since the diffracted light generated by the first andsecond metal wirings M1 and M2 reaches the photodiodes with a smallhorizontal diffraction angle, light collection efficiency of thephotodiodes is improved. Moreover, the two-layer wiring structureenables it to have an increased production yield. As the number ofwiring layers increases, the production yield decreases.

In the above example, although the horizontal wirings are formed by thefirst-layer metal wirings M1 and the vertical wirings are formed by thesecond-layer metal wirings M2, the vertical wirings may be formed by thefirst-layer metal wirings M1 and the horizontal wirings may be formed bythe second-layer metal wirings M2. However, when the diffraction oflight, the light shielding of the floating diffusions FD1 and FD2, andthe like are considered, it is preferable that the horizontal wiringsincluding the readout wirings 261 to 268 are formed by the first-layermetal wirings M1 and the vertical wirings are formed by the second-layermetal wirings M2.

Using eight pixels as one sharing unit, the gates of the readouttransistors Tr11 to Tr18 can be independently controlled via the readoutwirings 261 to 268 which are connected to the readout gate electrodes221 to 228 of the readout transistors Tr11 to Tr18. Since the gates canbe controlled independently, addition of necessary pixels to the eightpixels can be made easy. This pixel addition is performed within thefloating diffusions FD1 and FD2 of one sharing unit 21. For example,when the RGB pixels are arranged in the Bayer arrangement, any pixels ofthe same color in the eight pixels can be added. Alternatively, whenfour pixels of white (W), red (R), green (G), and blue (B) are arranged,pixels of any two colors (e.g., white (W) and green (G)) in the eightpixels may be added. Besides this, other pixel addition methods arepossible. That is, various pixel addition methods are possible such asaddition of a pixel in the first structural portion 23 and a pixel inthe second structural portion 25, addition of pixels in the firststructural portion, or addition of pixels in the second structuralportion. Furthermore, pixels on the vertical rows may be thinned out.

Since the pixels are laid out in a sharing unit with 2 pixels by 4pixels, respectively, in horizontal and vertical directions, pixels areread in units of 2 by 1 pixels, respectively, in row and columndirections. Thus, the area of the column signal processing circuit canbe decreased by half, and different gains for each color can be achievedin a relatively simple manner. Therefore, a chip area becomes small.

With reference to FIG. 50, a reference example of a solid-state imagingdevice 118 is illustrated in which a plurality of pixels 114 is arrangedin a two-dimensional array, a vertical signal line 116 and a powersupply wiring 117 are disposed for every column of the pixels 114, andunit column signal processing circuits 119 are arranged for each columnof the pixels. On the contrary, in this embodiment, as illustrated inFIG. 49, one sharing unit 140 is composed of eight pixels 114 in total(2 pixels by 4 pixels, respectively, in horizontal and verticaldirections), a vertical signal line 141 and a power supply wiring 142are provided for each sharing unit, and unit column signal processingcircuits 143 are arranged for each sharing unit. That is to say, sincethe vertical signal line 141 and the power supply wiring 142 which arewired in the longitudinal direction are disposed every two columns ofthe pixels, the unit column signal processing circuits 143 can be laidout at a pitch (dimension) of approximately twice the pixel pitch, andthus the area in the longitudinal direction is reduced.

On the other hand, in the MOS solid-state imaging devices, when signalsare amplified by amplification transistors, 1/f noise (flicker noise)the power spectrum of which is inversely proportional to the frequency fis generated because of a trap level in a gate insulating film of theamplification transistor. This 1/f noise generated in the amplificationtransistor has a great influence on image quality.

In this embodiment, the length of the amplification gate electrode 32 ofthe amplification transistor Tr3 is equal to or larger than one pixelpitch; therefore, the gate length is equal to or larger than one pixelpitch, in this example, close to two pixel pitches. Therefore, the 1/fnoise can be reduced. The 1/f noise can be expressed using Equation 1below.

$\begin{matrix}{\overset{\_}{V_{n}^{2}} = {\frac{K}{C_{ax}} \cdot \frac{1}{W \cdot L} \cdot {\int^{f_{c}}{\frac{1}{f}{df}}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In the equation, K is a process-dependent coefficient (which is relatedto electron capture/emission at the interface of a gate insulatingfilm), Cox is a capacitance of the gate insulating film, L is a gatelength (channel length) of a transistor, and W is a gate width (channelwidth). The power spectrum (mean-square noise voltage) of the 1/f noiseis given by Equation 1.

As clear from Equation 1 above, since the amplification gate electrode32 (namely, the gate length) of the amplification transistor Tr3 islong, it can be understood that the 1/f noise is decreased.

Since the drain region 31D of the amplification transistor Tr3 isconnected to the power supply wiring 36 which is wired in the verticaldirection, the value of current supplied to the amplificationtransistors on a selected row is not increased but can be maintained atan appropriate value. When the drain region 31D of the amplificationtransistor is connected to a power supply wiring which is wired in thehorizontal direction, it is necessary to supply current to amplificationtransistors of all the pixels on one selected row, which may necessitatean excessively large driving capability and is thus difficult toimplement.

Since sharing units with a 2 by 4 pixel arrangement are arranged in atwo-dimensional array, pixels can be read in a dot-sequential mannerfrom the end of the first row. However, when sharing units with a 4 by 2pixel arrangement are arranged in a two-dimensional array,post-processing is made difficult, and thus, it is difficult to readpixels in a dot-sequential manner.

In this embodiment, it is preferable that the number of wiring layers onthe peripheral circuit portion is two or more. Moreover, when the numberof wiring layers is different from the pixel portion to the peripheralcircuit portion, it is preferable that the insulating film on thetop-layer wiring in the pixel portion is formed to be thicker than theinsulating film on the top-layer wiring in the peripheral circuitportion. In the peripheral circuit region, the circuit area can bedecreased by increasing the number of wiring layers. However, in thepixel region, since it becomes difficult for the photodiode to collectlight when as the number of wiring layers increases, it is necessary todecrease the number of wiring layers. Furthermore, even when the numberof wiring layers in the pixel portion is small, since the collectionefficiency for oblique light decreases if the distance from thetop-layer wiring to the on-chip lenses provided for each pixel isincreased, it is preferable to decrease the thickness of the insulatingfilm on the top-layer wiring.

Embodiment 2: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 6, a solid-state imaging device, namely an MOSsolid-state imaging device, according to Embodiment 2 of the presentinvention is illustrated. FIG. 6 illustrates only the layout of afirst-layer metal when the first-layer metal wirings M1 are formed. Asolid-state imaging device 102 according to Embodiment 2 includes lightshielding portions 45 which are provided for each sharing unit 21 andwhich are formed by the first-layer metal on each of the floatingdiffusions FD1 and FD2. That is to say, in the solid-state imagingdevice, 102 the readout wirings 261 to 268, the reset wiring 27, thepower supply wiring 29 that is connected to the drain region of thereset transistor Tr2 are formed by the first-layer metal wirings M1.Moreover, the light shielding portions 45 are formed by the first-layermetal wirings M1 so as to cover the floating diffusions FD1 and FD2.Since other configurations are the same as those described in Embodiment1, portions corresponding to those in FIG. 2 will be denoted by the samereference numerals, and description thereof will be omitted.

According to the solid-state imaging device 102 of Embodiment 2, thelight shielding portions 45 formed by the first-layer metal wirings M1are formed on the floating diffusions FD1 and FD2 with a narrow spacingfrom the readout wirings 262 and 263, and 266 and 267, respectively. Dueto this configuration, it is possible to achieve more reliable shieldingof the floating diffusions FD1 and FD2. In addition to this, the sameadvantages as those described in Embodiment 1 can be obtained.

In Embodiment 1 described above, with the miniaturization of pixels,when the width of each of the four readout wirings 261 to 264 (or 265 to268) and the spacing between adjacent wirings are decreased, lightbecomes unable to pass therethrough. That is to say, when the spacingbetween the readout wirings is decreased to be equal to or smaller thana diffraction limit, light does not pass through the interwiringspacing. Therefore, the region where these four readout wirings 261 to264 (or 265 to 268) are arranged performs the role of a light shieldingportion. When the pixels are miniaturized further, the spacing betweenthe readout wirings is further decreased to be further smaller than thediffraction limit. Therefore, in Embodiment 1, as the width of eachreadout wiring and the spacing between the readout wirings decrease, theaperture area of each of the photodiodes PD1 to PD8 can be increased,and thus the sensitivity can be improved.

The diffraction limit will be described with reference to FIGS. 7 and 8.In FIG. 7, “a” is an aperture width between wirings 111. FIG. 7illustrates a light intensity distribution when light (in this example,green light having wavelength λ of 530 nm) is passed through an aperture112 so that a photodiode PD is irradiated with the light. The intensityof the light having reached the photodiode PD peaks at an aperturecenter O, decreases as it becomes distant from the aperture center, andbecomes 0 at a point P. This point P is referred to as a first darkring. As the aperture 112 is narrowed, the light is diffracted more, sothat the distance (OP) in the light intensity distribution from theaperture center O to the first dark ring P increases, and the peak ofthe light intensity decreases.

FIG. 8 illustrates the case of increasing the distance (OP). FIG. 8 is agraph when a dimension D from the center to the end of the photodiode PDin FIG. 7 is 600 nm, and green light Lg (wavelength λ: 530 nm) is madeincident. The aperture width a at which the distance (OP) becomes themaximum is the diffraction limit. For example, as the distance (OP)becomes larger than ½ of the pixel pitch, it becomes difficult for thephotodiode PD to collect light. When the aperture width is equal to orsmaller than the diffraction limit, light is diffracted, so that lightis not collected by the photodiode PD; that is, light will not enter thephotodiode PD.

When light is diffracted with the aperture 112 moved closer to thephotodiode PD, the light can be collected by the photodiode PD withoutincreasing the distance (OP).

In the case of a multi-layer wiring structure, since light is diffractedat a lower-layer wiring as the distance (OP) increases, the distance(OP) will increase further and the peak will decrease. Therefore, as thenumber of wiring layers decreases, the distance (OP) in the intensitydistribution of the light having reached the photodiode PD decreases.

Embodiment 3: Exemplary Configuration of Solid-State Imaging Device

With reference to FIGS. 9 and 10, a solid-state imaging device, namelyan MOS solid-state imaging device, according to Embodiment 3 of thepresent invention is illustrated. FIG. 9 illustrates a main part of alayout of a pixel portion. FIG. 10 illustrates the pattern of thefirst-layer wirings. A solid-state imaging device 103 according toEmbodiment 3 has one sharing unit 21 in which at least one of thereadout wirings in unit pixels is disposed within the regions of thephotodiodes PD, and the regions of the photodiodes PD are disposed onboth sides of and right below the one readout wiring.

In this example, in one sharing unit 21, among a plurality of readoutwirings on the same layer which are disposed within the pixel pitch P,one readout wiring is spaced apart from the other readout wirings. Thisreadout wiring is disposed at a distance d2 from the other readoutwirings, wherein the distance d2 is larger than a minimum spacing d1between the readout wirings on the same layer which occur repeatedly inone sharing unit 21. The minimum spacing d1 is a spacing which is equalto or smaller than a so-called diffraction limit, at which light doesnot substantially pass therethrough. The distance (spacing) d2 is adistance which exceeds the diffraction limit, at which light issubstantially allowed to pass therethrough.

In other words, the solid-state imaging device 103 of this embodimenthas a configuration in which one readout wiring in one sharing unit 21is disposed on the photodiodes PD so as to be spaced from the otherreadout wirings by a distance exceeding the diffraction limit.Specifically, as illustrated in FIGS. 9 and 10, in the first structuralportion 23, among the four readout wirings 261 to 264, the readoutwiring 261 is disposed so as to correspond to the position, for example,near the centers of the photodiodes PD1 and PD2, and the readout wiring264 is disposed so as to correspond to the position, for example, nearthe centers of the photodiodes PD3 and PD4. In the second structuralportion 25, among the four readout wirings 265 to 268, the readoutwiring 265 is disposed so as to correspond to the position, for example,near the centers of the photodiodes PD5 and PD6, and the readout wiring268 is disposed so as to correspond to the position, for example, nearthe centers of the photodiodes PD7 and PD8.

The minimum spacing (distance) d1 between the readout wirings 262 and263 and the minimum spacing (distance) d1 between the readout wirings266 and 267 are set to be equal to or smaller than the diffractionlimit. The distance d2 between the readout wirings 261 and 262 and thedistance d2 between the readout wirings 264 and 263 are set to exceedthe diffraction limit. Moreover, the distance d2 between the readoutwirings 265 and 266 and the distance d2 between the readout wirings 268and 267 are set to exceed the diffraction limit. Although the readoutwirings 261, 264, 265, and 268 may only have to be disposed on thephotodiodes PD so as to be spaced by a distance exceeding thediffraction limit from the other readout wirings, they are preferablydisposed near the centers of the photodiodes PD. That is to say, thereadout wirings are preferably laid out so that the readout wirings 261,264, 265, and 268 are disposed at the optical center O of a pixel (orthe center of the pixel pitch) as illustrated in FIG. 12.

The readout wiring 261 is connected to the readout gate electrode 221via an extension portion 261 a. The readout wirings 262 and 263 areconnected to the readout gate electrodes 222 and 223, respectively. Thereadout gate electrode 264 is connected to the readout gate electrode224 via an extension portion 264 a. The readout wiring 265 is connectedto the readout gate electrode 225 via an extension portion 265 a. Thereadout wirings 266 and 267 are connected to the readout gate electrodes226 and 227, respectively. The readout gate electrode 268 is connectedto the readout gate electrode 228 via an extension portion 268 a.

Since other configurations are the same as those described in Embodiment1, portions corresponding to those in FIG. 2 will be denoted by the samereference numerals, and description thereof will be omitted. However, inthis example, although the readout gate electrodes 221 to 228 have aslightly different shape from the shape illustrated in FIG. 2, they canbe said to have the same shape.

According to the solid-state imaging device 103 of Embodiment 3, thereadout wirings 261, 264, 265, and 268 are shifted so as to be disposedrespectively on the photodiodes PD1 and PD2, the photodiodes PD3 andPD4, the photodiodes PD5 and PD6, and the photodiodes PD7 and PD8. Dueto this configuration, the aperture area of each of the photodiodes PD1to PD8 is increased by an amount corresponding to one spacing betweenthe readout wirings, compared to Embodiment 1 illustrated in FIG. 2. Atthis time, light at the vicinity of the readout wiring near the centersof the photodiodes PD curves towards the backside of the readout wiringbecause of diffraction to be collected by the photodiodes PD.

This phenomenon will be described with reference to the schematicdiagram of FIG. 12. FIG. 12 illustrates the portion of the photodiodePD1. The photodiode PD1 is formed in a semiconductor substrate 70, andthe readout wiring 262 and the reset wiring 27, which are formed by thefirst-layer metal wirings M1, and the second-layer metal wirings M2 aredisposed thereon via the interlayer insulating film 39 so as to definean aperture of the photodiode PD1. An on-chip connector housing 47 andan on-chip microlens 48 are formed on this two-layer wiring structurevia a planarization film (not illustrated). Furthermore, the readoutwiring 261 which is formed by the first-layer metal wirings is disposednear the center of the photodiode PD1.

Light La incident right above the readout wiring 261 is reflected by thereadout wiring. However, since the readout wiring 261 disposed near thecenter of the photodiode PD1 has a very small width, light Lb incidentat the vicinity of the readout wiring 261 is diffracted by the readoutwiring 261 to curve towards the backside of the readout wiring 261 to becollected by the photodiode PD1. Since the incident light is condensedby the on-chip microlens 48, a wave front 49 propagating towards thecenter of the photodiode PD1 is dominant. For this reason, when light isdiffracted by the readout wiring 261, the light curving towards thecenter of the backside is dominant.

On the other hand, a solid-state imaging device is known which increaseslight collection efficiency by using a combination of an on-chipmicrolens and an inner-layer lens. However, it becomes difficult to formthe inner-layer lens as the pixel size is further miniaturized. InEmbodiment 3, since one of the readout wirings is disposed near thecenter of the photodiode PD so that incident light is diffracted by thereadout wiring to be collected by the photodiode, the readout wiring atthe center performs the role of the inner-layer lens, whereby lightcollection efficiency can be improved.

In Embodiment 3, since the light collection efficiency is improved, itis possible to achieve further improvement in the sensitivity. Inaddition to this, the same advantages as those described in Embodiment 1can be obtained.

Embodiment 4: Exemplary Configuration of Solid-State Imaging Device

Embodiment 4 illustrates another example of one sharing unit 21 in whichat least one of the readout wirings in unit pixels is disposed withinthe regions of the photodiodes PD, and the regions of the photodiodes PDare disposed on both sides of and right below the one readout wiring.

When the pixels are further miniaturized, a configuration may beconsidered in which the photodiodes of the colors red, green, and blue(RGB) are disposed at different positions in a depth direction thereof,and the photodiodes of the RGB colors are arranged so as to overlappartially each other in a top plan view thereof so as to increase alight receiving area. At this time, since a region where no photodiodeis formed exists between photodiodes of adjacent pixels, it is difficultto arrange all of the four readout wirings between pixels. Embodiment 4provides a solid-state imaging device applicable to such a case.

With reference to FIGS. 13 and 14, a solid-state imaging device, namelyan MOS solid-state imaging device, according to Embodiment 4 of thepresent invention is illustrated. FIG. 13 illustrates a main part of alayout of a pixel portion. However, on a plan view, the photodiodes arepartitioned for each pixel for convenience's sake. FIG. 14 illustrates aconfiguration of a photodiode in a semiconductor substrate.

As illustrated in FIG. 13, a solid-state imaging device 104 according toEmbodiment 4 includes one sharing unit 21 in which all the readoutwirings 261 to 268 on the same layer are disposed at a distance d3 fromeach other in one sharing unit 21, wherein the distance d3 is largerthan the minimum spacing d1 (see FIG. 9). In other words, in thesolid-state imaging device 104 of this embodiment, the readout wirings261 to 268 are disposed at a distance exceeding the diffraction limitfrom each other. When diffraction of light is considered, it ispreferable that the readout wirings 261 to 268 are sufficiently spacedfrom each other to be disposed at an equal pitch (spacing), for exampleso that the distance between the wiring is maximized. Moreover, adjacenttwo wirings of the readout wirings 261 to 268 are disposed on thephotodiodes PD1 and PD2, the photodiodes PD3 and PD4, the photodiodesPD5 and PD6, and the photodiodes PD7 and PD8, respectively. Although nowillustrated in the figure, the readout wirings 261 to 268 are connectedto the corresponding readout gate electrodes 221 to 228 via extensionportions, respectively, similar to Embodiment 3.

Next, photodiodes PD with a Bayer arrangement, for example, will bedescribed. The photodiodes PDr, PDg, and PDb of the colors red (R),green (G), and blue (B) are formed, for example, in a semiconductor wellregion 52 of second conductivity type (e.g., p type) which is formed ina semiconductor substrate 51 of first conductivity type (e.g., n type),as illustrated in FIG. 14. The photodiodes PDr, PDg, and PDb are formedby an n-type semiconductor region 53 and a p-type semiconductor region54 which is formed on the n-type semiconductor region 53.

Since light having a blue wavelength is absorbed in a shallow region,the photodiode PDb of a blue pixel is formed close to a surface side ofthe semiconductor well region 52. Since light having a green wavelengthis absorbed at a deeper position than the light having a bluewavelength, the photodiode PDg of a green pixel is formed so as toextend partially from the surface of the semiconductor well region to aregion right below the photodiode PDb of the blue pixel. Since lighthaving a red wavelength is absorbed at a deepest position, thephotodiode PDr of a red pixel is formed so as to extend partially fromthe surface of the semiconductor well region to a region right below thephotodiode PDg of the green pixel. In this example, the photodiode PDgof the green pixel and the photodiode PDr of the red pixel are formed soas to pass each other in a depth direction thereof. As illustrated inFIG. 14, since the photodiodes PDr, PDg, and PDb of each pixel areformed so as to overlap each other in a substrate-depth direction, aregion where no photodiode is formed does not exist between thephotodiodes of adjacent pixels.

Since other configurations are the same as those described in Embodiment1, portions corresponding to those in FIG. 2 will be denoted by the samereference numerals, and description thereof will be omitted.

According to the solid-state imaging device 104 of Embodiment 4, sincethe photodiodes of each pixel of the colors red, green, and blue areformed at different positions in the depth direction of thesemiconductor substrate 51, a color separation is realized within thesemiconductor substrate. That is to say, prevention of a color mixturecan be achieved within the semiconductor substrate 51. Moreover, sincethe readout wirings 261 to 268 which are connected to the readouttransistors Tr11 to Tr18 of each pixel are spaced from each other at adistance exceeding the diffraction limit, it is possible to furtherincrease the aperture area of each of the photodiodes PD1 to PD8. Thereadout wirings 261 to 268 provide the same effects as those describedin FIG. 12. Therefore, it is possible to improve the sensitivity evenwhen the pixels are further miniaturized. In addition to this, the sameadvantages as those described in Embodiment 1 can be obtained.

Embodiment 5: Exemplary Configuration of Solid-State Imaging Device

With reference to FIGS. 15A and 15B, a solid-state imaging device,namely an MOS solid-state imaging device, according to Embodiment 5 ofthe present invention is illustrated. FIGS. 15A and 15B illustrate amain part of a layout of a pixel portion, respectively, illustrating thepatterns of first-layer wirings and second-layer wirings in explodedplanar views. A solid-state imaging device 105 according to Embodiment 5includes dummy wirings which are formed by the first-layer wirings andthe second-layer wirings as illustrated in FIG. 15B in order to realizea good symmetry in the wirings of one sharing unit 21. That is to say,by the same first-layer metal wirings M1, the readout wirings 261 to268, the reset wiring 27, and the power supply wiring 29, which are thehorizontal wirings, are formed, and at the same time, divided dummywirings 56 to which voltage is not applied are formed on both left andright sides of the photodiodes PD1 to PD8. Moreover, by the samesecond-layer metal wirings M2, the connection wiring 28, the verticalsignal line 35, and the power supply wiring 36, which are the verticalwirings, are formed, and at the same time, divided dummy wirings 57 towhich voltage is not applied are formed on both upper and lower sides ofthe photodiodes PD1 to PD8.

Since other configurations are the same as those described in Embodiment1, portions corresponding to those in FIG. 2 will be denoted by the samereference numerals, and description thereof will be omitted.

According to the solid-state imaging device 105 of Embodiment 5, inaddition to the horizontal wirings and the vertical wirings, the dummywirings 56 and 57, which are formed by the first-layer metal wirings M1and the second-layer metal wirings M2, respectively, are formed so thatthe photodiodes PD1 to PD8 are surrounded by these wirings. Due to thisconfiguration, the photodiodes PD1 to PD8 are surrounded by the metalwirings on the same layer with a good symmetry, and thus a color mixturedue to diffraction of light can be prevented. In addition to this, thesame advantages as those described in Embodiment 1 can be obtained.

Embodiment 6: Exemplary Configuration of Solid-State Imaging Device

With reference to FIGS. 16A and 16B, a solid-state imaging device,namely an MOS solid-state imaging device, according to Embodiment 6 ofthe present invention is illustrated. FIGS. 16A and 16B illustrates amain part (one sharing unit) of a layout of a pixel portion. Embodiment6 illustrates another layout in which dummy wirings are disposed.

As illustrated in FIG. 16A, a solid-state imaging device 106 accordingto Embodiment 6 includes the dummy wirings 57 which are formed by thesecond-layer metal wirings M2 and are disposed so as vertically tosandwich each of the photodiodes PD1 to PD8. The dummy wirings 57 aredisposed to be divided at various positions including positionscorresponding to regions on the readout wirings 261, 263, 266, and 267formed by the first-layer metal wirings M1, a position corresponding toa region on the amplification gate electrode 32, and positionscorresponding to regions on the reset wiring 27 and the power supplywiring 29 which are formed by the first-layer metal wirings M1.

Here, the reset wiring 27 formed by the first-layer metal wirings M1 isdivided into a reset wiring part 27A having one end thereof connected tothe reset gate electrode 34 and a reset wiring part 27B that is notconnected to the reset gate electrode 34, as illustrated in FIG. 16B.The reset wiring parts 27A and 27B are connected by a connection wiring27C which is formed by the second-layer metal wirings M2, whereby thereset wiring 27 is formed. Moreover, the light shielding portions 45that shield the upper portions of the floating diffusions FD1 and FD2are formed to be integral with the floating diffusions FD1 and FD2, theamplification gate electrode 32, and the connection wiring 28 that isconnected to the source region 33S of the reset transistor Tr2. Thelight shielding portions 45 are formed by the second-layer metal wiringsM2 by expanding portions of the connection wiring 28 corresponding tothe contact portions with the floating diffusions FD1 and FD2.

Since other configurations are the same as those described in Embodiment1, portions corresponding to those in FIG. 2 will be denoted by the samereference numerals, and description thereof will be omitted.

According to the solid-state imaging device 106 of Embodiment 6, sincethe dummy wirings 57 formed by the second-layer metal wirings M2 aredisposed, the metal wirings are disposed around each of the photodiodesPD1 to PD8 with a good symmetry. Due to this configuration, similar toEmbodiment 5, each of the photodiodes PD1 to PD8 is surrounded by thedummy wirings 57 and other wirings, and thus a color mixture due todiffraction of light can be prevented. In addition to this, the sameadvantages as those described in Embodiment 1 can be obtained.

Embodiment 7: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 17, a solid-state imaging device, namely an MOSsolid-state imaging device, according to Embodiment 7 of the presentinvention is illustrated. FIG. 17 illustrates a main part (one sharingunit) of a layout of a pixel portion. A solid-state imaging device 107according to Embodiment 7 includes the photodiodes PD1 to PD8 which arenot square in shape but have a shape with rounded corners.

When the photodiodes PD1 to PD8 are formed using an ion implantationmethod, a resist mask is used as an ion implantation mask. Since thisresist mask is formed by a photolithography technique, an aperture islikely to have rounded corners and is hardly made perfectly square inshape. By using such a resist mask, the photodiodes PD1 to PD8 can beformed approximately square in shape with rounded corners.

Since other configurations are the same as those described in Embodiment1, portions corresponding to those in FIG. 2 will be denoted by the samereference numerals, and description thereof will be omitted.

According to the solid-state imaging device 107 of Embodiment 7, sincethe photoresist has rounded corners, each of the photodiodes PD1 to PD8can be formed with rounded corners. When the source region 31S and thedrain region 31D of the amplification transistor Tr3, the source region33S and the drain region 33D of the reset transistor Tr2, and the likeare disposed in a region surrounded by the rounded corners, it ispossible to expect an advantage of minimizing generation of anineffective region. Moreover, damage incurred during the ionimplantation does not have an influence on the photodiodes. In additionto this, the same advantages as those described in Embodiment 1 can beobtained.

The configuration of rounding the corners of the photodiode inEmbodiment 7 can be applied to Embodiments 2 to 5 described above andEmbodiments which will be described later.

Embodiment 8: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 18, a solid-state imaging device, namely an MOSsolid-state imaging device, according to Embodiment 8 of the presentinvention is illustrated. FIG. 18 illustrates a main part (one sharingunit) of a pixel portion. A solid-state imaging device 108 according toEmbodiment 8 includes one sharing unit 21 in which dot-shaped structures61 having a light condensing function are formed at positionscorresponding to each region on each of the photodiodes PD1 to PD8,preferably at positions near the centers of each photodiode. Thedot-shaped structures 61 are formed in an island-like shape, to whichvoltage is not applied, and are spaced from other wirings at a distanceexceeding the diffraction limit. When the dot-shaped structures 61 areformed in a two-layer wiring structure, they are formed by any one ofthe metals on the same layer as the first-layer metal wirings M1 and themetal on the same layer as the second-layer metal wirings M2. Thedot-shaped structures 61 are preferably formed by the metal on the samelayer as the first-layer metal wirings M1.

The dot-shaped structures 61 are preferably formed with a film thicknessallowing light to pass therethrough. The dot-shaped structures 61 arepreferably formed by a thin metal film having a smaller thickness thanthe thickness of the first-layer metal wirings M1 and the second-layermetal wirings M2.

The dot-shaped structures 61 may be formed, for example, in arectangular shape, a circular shape, a cross shape, a polygonal shape,and any other geometrical shapes. The dot-shaped structure 61 may beprovided one, two, or plurally more than two in number. The dot-shapedstructures may be formed of Cu, Al, SiON, SiN, SiC, TiN, ITO, TaN, W,WSi, WN, and the like.

Since other configurations are the same as those described in Embodiment1, portions corresponding to those in FIG. 2 will be denoted by the samereference numerals, and description thereof will be omitted.

With reference to FIGS. 19A and 19B, an example of a formation method ofthe dot-shaped structure 61. As illustrated in FIG. 19A, trenches 63 and64 having the same depth are formed on a surface of an interlayerinsulating film 62 at positions where a dot-shaped structure and awiring are to be formed, respectively. A Cu film 65 is buried in thetrenches 63 and 64 via a barrier metal, for example. Subsequently, aplanarization process is performed, and the Cu film 65 buried in thetrench 63 corresponding to the dot-shaped structure is selectivelyetched together with the barrier metal so as to have a predeterminedthickness as illustrated in FIG. 19B. In this way, a Cu wiring is formedin the trench 64, and a dot-shaped structure 61 formed by the thin Cufilm is formed in the trench 63.

With reference to FIGS. 20A and 20B, another example of a formationmethod of a dot-shaped structure is illustrated. As illustrated in FIG.20A, a shallow trench 67 is formed on a surface of an interlayerinsulating film 62 at a position where a dot-shaped structure is to beformed, and a trench 68 deeper than the trench 67 is formed on thesurface of the interlayer insulating film 62 at a position where awiring is to be formed. Subsequently, as illustrated in FIG. 20B, a Cufilm 65 is buried in the trenches 67 and 68 via a barrier metal.Thereafter, a planarization process is performed, whereby a dot-shapedstructure 61 formed by the thin Cu film is formed in the trench 67, anda Cu wiring 66 is formed in the trench 68.

The Cu wiring 66 is formed, for example, as the horizontal wiring (thereadout wirings 261 to 268, the reset wiring 27, and the power supplywiring 29) which is formed by the first-layer metal wirings.

According to the solid-state imaging device 108 of Embodiment 8, thedot-shaped structures 61 which are separately disposed near the centersof the photodiodes PD1 to PD8 have the same light condensing function asthe above-described function of the readout wirings 261, 264, 265, and268 described in Embodiment 3. As illustrated in the schematic diagramof FIG. 21, light is diffracted at the vicinity of the dot-shapedstructure 61 to curve towards the backside of the dot-shaped structure61 to be collected by the photodiode PD. In this example, due tointerference of light, light intensity increases at a position rightbelow the dot-shaped structure 61. Moreover, the diffracted light Lc andthe transmitted light Ld having passed through the dot-shaped structure61 are added, and the light intensity increases further. The dot-shapedstructure 61 has the function of an inner-layer lens.

In the example above, although the dot-shaped structure 61 is formed ina single-layer metal structure, the dot-shaped structure 61 may beformed in a multi-layer metal structure (e.g., two, three, andfour-layer structure) at the same position via an interlayer insulatingfilm. When the dot-shaped structure 61 is formed in a multi-layerstructure, it is preferable that a dot width decreases as it goestowards a lower layer. When the dot-shaped structure 61 is formed in amulti-layer structure, light is first made curved towards an upper-layerdot-shaped structure and then curves towards a lower-layer dot-shapedstructure to be collected by the photodiode.

As illustrated in FIG. 22, in order to prevent diffusion of Cu, an SiCfilm 68, for example, is formed on the entire surface of a wiring 66 anda dot-shaped structure 61, which are formed by first-layer Cu metal, anda wiring 67 formed by second-layer Cu metal. The SiC film 68 may remainformed on a portion corresponding to a region on the photodiode.However, as illustrated in FIG. 22, when there are two layers of the SiCfilm 68, there is concern that a part Lf of incident light undergoesmultiple reflection between the two layers of the SiC film 68, which maylead to ripples and decrease the sensitivity.

For this reason, as illustrated in FIG. 23, it is preferable to removeselectively a portion of the second-layer SiC film 68 corresponding tothe region on the photodiode. It was found from the simulation resultsthat it is not necessary to etch selectively an entire layer of the SiCfilm 68 corresponding to the region on the photodiode, but it isnecessary to etch selectively only the second-layer SiC film 68. Bydoing so, the multiple reflection is reduced, whereby occurrence ofripples is suppressed, and the sensitivity is improved. Here, since theremoval of the second-layer SiC film 68 can be realized by etching usinga direct mask alignment, it is possible to etch and remove the portionof the SiC film corresponding to the photodiode to the fullest extent.For this reason, it is possible to increase an aperture size anddecrease a length w1 of a canopy portion 69, and accordingly, theoccurrence of multiple reflection can be suppressed.

When a waveguide is provided as another means for increasing the lightcollection efficiency, as illustrated in FIG. 24, it is necessary toetch selectively and remove an entire layer, in this case, the first andsecond-layer SiC films 68, of the portion corresponding to the region onthe photodiode. At this time, since the first and second-layer SiC films68 are etched via an indirect mask alignment, they are etched with amargin considering alignment errors. For this reason, an aperture sizeobtained thus is small, the length w2 of the canopy portion 69increases, and thus the suppression effect of multiple reflection isless than that in FIG. 22.

The dot-shaped structure 61 shifts its position between the centralportion of the pixel portion and the periphery of the pixel portion.Since light is incident approximately right above itself in the centralportion of the pixel portion, the dot-shaped structure 61 is disposed atthe center. Since oblique light is incident in the periphery of thepixel portion, the dot-shaped structure 61 is shifted from its optimumposition in the central portion of the pixel portion by a distancecorresponding to the amount of shift between the on-chip microlens andeach pixel.

Embodiment 9: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 25, a solid-state imaging device, namely an MOSsolid-state imaging device, according to Embodiment 9 of the presentinvention is illustrated. FIG. 25 illustrates a main part (one sharingunit) of a pixel portion. A solid-state imaging device 109 according toEmbodiment 9 includes wirings 71 which do not have a wiring function andwhich are disposed at positions corresponding to the regions on thephotodiodes PD1 to PD8, preferably, so as to pass along the vicinitiesof the centers of the photodiodes. The wirings 71 have the same lightcondensing function as an inner-layer lens similar to theabove-described readout wirings 261, 264, 265, and 268 of Embodiment 3and the dot-shaped structures 61 of Embodiment 8. As illustrated in FIG.25, the wirings 71 may be provided for each sharing unit 21 and may becommonly provided to the photodiodes of the entire pixels on one row.The wirings 71 are simultaneously formed by the same metal wirings asthe readout wirings 261 to 268. Alternatively, the wirings 71 may beformed to be thinner than the readout wirings similar to the dot-shapedstructures 61.

Since other configurations are the same as those described in Embodiment1, portions corresponding to those in FIG. 2 will be denoted by the samereference numerals, and description thereof will be omitted.

According to the solid-state imaging device 109 of Embodiment 9, sincelight is condensed by the diffracting effect of the wirings 71 asdescribed above in FIGS. 12 and 21, the light collection efficiency isimproved, and thus it is possible to achieve further improvement in thesensitivity. In addition to this, the same advantages as those describedin Embodiment 1 can be obtained.

Embodiment 10: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 26, a solid-state imaging device, namely an MOSsolid-state imaging device, according to Embodiment 10 of the presentinvention is illustrated. FIG. 26 is a cross-sectional viewschematically showing a sectional pixel structure of one sharing unitusing a red pixel as a representative pixel. Other pixels (e.g., greenpixels and blue pixels) have a similar sectional structure.

Similar to Embodiment 1 illustrated in FIG. 2, a solid-state imagingdevice 110 according to Embodiment 10 includes one sharing unit 21 inwhich photodiodes PD (PD1 to PD8) of 8 pixels in total (2 pixels by 4pixels, respectively, in horizontal and vertical directions) and tenpixel transistors are arranged. The readout wirings 261 to 268, whichare connected to the readout transistors Tr11 to Tr18, and the resetwiring 27 and the power supply wiring 29, which are connected to thereset transistor Tr2, are wired in the transverse direction by thefirst-layer metal wirings M1. The connection wiring 28, and the convexlens elements 35 and the power supply wiring 36, which are connected tothe amplification transistor Tr3, are wired in the longitudinaldirection by the second-layer metal wirings M2.

In this embodiment, as illustrated in FIG. 26, a two-layer wiringstructure 72 is formed on a semiconductor substrate 70 on which aphotodiode (a photodiode of the red pixel is used as a representativeexample) PDr and pixel transistors are formed. That is to say, first andsecond-layer metal wirings M1 and M2 are formed via an interlayerinsulating film 39. The metal wirings M1 and M2 are formed with a Cuwiring 73 which is formed via a barrier metal and an SiC film 74 forpreventing diffusion of Cu as described above.

In particular, in this embodiment, a color filter 75 (in this figure, ared filter) is buried in the interlayer insulating film 39 at a positionof the two-layer wiring structure 72 corresponding to a region on thephotodiode PDr. A planarized passivation film 76 is formed on thesurface of a structure thus obtained. An on-chip microlens may not beformed on the passivation film 76. Alternatively, an on-chip microlensmay be formed on the passivation film 76.

Other pixels (e.g., green pixels and blue pixels) have a similarsectional structure. Since other configurations are the same as thosedescribed in Embodiment 1, description of the same layout as that inFIG. 2 will be omitted.

According to the solid-state imaging device 110 of Embodiment 10, thecolor filter 75 is buried in the two-layer wiring structure 72 by usinga configuration such that the horizontal and vertical wirings formingthe respective wirings are formed by the two-layer wiring structure 72having an overall height smaller than that of the related art wiringstructure (e.g., a four-layer wiring structure). Due to thisconfiguration, it is possible to prevent a color mixture. Moreover,since the height h1 from the photodiode PDr to the top surface of thecolor filter 75 is lower than the height of the related artconfiguration, it is possible to achieve further improvement in thelight collection efficiency. When the on-chip microlens is omitted, thestructure can be further simplified. In addition to this, the sameadvantages as those described in Embodiment 1 can be obtained.

Embodiment 11: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 27, a solid-state imaging device, namely an MOSsolid-state imaging device, according to Embodiment 11 of the presentinvention is illustrated. FIG. 27 illustrates a main part of a layout ofa pixel portion using a two-layer wiring structure. As illustrated inFIG. 27, a solid-state imaging device 113 according to Embodiment 11includes one sharing unit 81 which includes photodiodes PD (PD1 to PD8)of 8 pixels in total (2 pixels by 4 pixels, respectively, in horizontaland vertical directions) and eleven pixel transistors. Such sharingunits 81 are arranged in a two-dimensional array to form a pixel portion3. That is to say, similar to Embodiment 1, one sharing unit 81 is laidout in a so-called 8-pixel sharing structure with 2 pixels by 4 pixels,respectively, in horizontal and vertical directions, in which twostructural groups are arranged vertically, wherein one structural grouphas one floating diffusion FD which is shared by four photodiodes PD intotal (2 by 2 photodiodes, respectively, in horizontal and verticaldirections).

One sharing unit 81 includes 1.375 pixel transistors per pixel. Theeleven pixel transistors are specifically broken down into eighttransfer transistors Tr1 (Tr11 to Tr18), one reset transistor Tr2, oneamplification transistor Tr3, and one select transistor Tr4.

As illustrated in FIG. 27, the solid-state imaging device 113 accordingto Embodiment 11 includes the amplification transistor Tr3 and theselect transistor Tr4 which are disposed between the first structuralportion 23 and the second structural portion 25. The amplificationtransistor Tr3 includes a source region 31S, a drain region 31D, and anamplification gate electrode 32 as described above. The selecttransistor Tr4 includes a source region 83S, a drain region 83D, and aselect gate electrode 84 and is connected to the amplificationtransistor Tr3. The source region 83S of the select transistor Tr4 isthe same region as the drain region 31D of the amplification transistorTr3.

The vertical signal line 35 is connected to the source region 31S of theamplification transistor Tr3, and the power supply wiring 36 isconnected to the drain region 83D of the select transistor Tr4. Theselect gate electrode 84 of the select transistor Tr4 is connected to aselect wiring 85. The vertical signal line 35, the power supply wiring36, and the select wiring 85 are formed by the second-layer metalwirings M2 so as to extend in the longitudinal direction. In particular,the select gate electrode 84 of the select transistor Tr4 is connectedto the select wiring 85, which is formed by the second-layer metalwirings M2, via a connection line 85 a which is formed by thefirst-layer metal wirings M1.

Since other configurations are the same as those described in Embodiment1, portions corresponding to those in FIG. 2 will be denoted by the samereference numerals, and description thereof will be omitted.

With reference to FIG. 28, an equivalent circuit of one sharing unit 81according to Embodiment 13 is illustrated. In this equivalent circuit, aconfiguration where the select transistor Tr4 is connected between thepower supply wiring 36 and the drain of the amplification transistorTr3, and the select wiring 85 is connected to the select gate is addedto the equivalent circuit illustrated in FIG. 5. Other circuitconfigurations are the same as the circuit configurations illustrated inFIG. 5.

According to the solid-state imaging device 113 of Embodiment 11, sinceone sharing unit 81 has a structure with 8 pixels and 11 transistors,the number of pixel transistors per pixel can be decreased, andaccordingly, the aperture area of each of the photodiodes PD1 to PD8 canbe increased. Moreover, the wirings are formed in only a two-layerwiring structure, the first-layer metal wirings M1 are used for thewirings in the transverse direction, and the second-layer metal wiringsM2 are used for the wirings in the longitudinal direction, whereby theaperture area of the photodiode is defined by the vertical andhorizontal wirings. This wiring layout is not complex and does notinterfere with the aperture of the photodiode. As described above, sincethe aperture area of the photodiode can be increased, it is possible toimprove the sensitivity even when the pixels are miniaturized.Therefore, a solid-state imaging device with high sensitivity and highresolution can be obtained. In addition to this, the same advantages asthose described in Embodiment 1 can be obtained.

Embodiment 12: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 29 and FIGS. 30A to 30C, a solid-state imagingdevice, namely an MOS solid-state imaging device, according toEmbodiment 12 of the present invention is illustrated. FIG. 29illustrates a main part of a layout of a pixel portion using a two-layerwiring structure. FIGS. 30A to 30C are exploded planar views forunderstanding the patterns of first-layer wirings and second-layerwirings.

As illustrated in FIG. 29, similar to Embodiment 1, a solid-stateimaging device 115 according to Embodiment 12 includes one sharing unit21 which includes photodiodes PD (PD1 to PD8) of 8 pixels in total (2pixels by 4 pixels, respectively, in horizontal and vertical directions)and ten pixel transistors. Such sharing units 21 are arranged in atwo-dimensional array to form a pixel portion 3. The photodiodes PD1 toPD8, the readout transistors Tr11 to Tr18 forming the pixel transistors,and the amplification transistor Tr3 have the same configuration as thatof Embodiment 1.

In this embodiment, in particular, the reset transistor Tr2 isconfigured differently. That is to say, as illustrated in FIG. 30A, thesource region 33S and the drain region 33D of the reset transistor Tr2are disposed not in the longitudinal direction, but in the transversedirection, with respect to the reset gate electrode 34. Moreover, thereset transistor Tr2 is shifted in the transverse direction so as tooverlap between adjacent sharing units 21. Furthermore, the reset wiring27 connected to the reset gate electrode 34 of the reset transistor Tr2and the power supply wiring 29 connected to the drain region 33D areformed in parallel to each other in the transverse direction using thefirst and second-layer metal wirings M1 and M2, respectively. The resetwiring 27 and the power supply wiring 29 are disposed on the reset gateelectrode 34, and preferably, are formed with a width smaller than thewidth of the reset gate electrode 34.

First, as illustrated in FIG. 30A, an array of photodiodes PD1 to PD8corresponding to an arrangement of 2 pixels by 4 pixels, the floatingdiffusions FD1 and FD2, and the readout transistors Tr11 to Tr18 havingthe readout gate electrodes 221 to 228 are formed. Furthermore, thereset transistor Tr2 and the amplification transistor Tr3 are formed,wherein the reset transistor Tr2 has the source region 33S and the drainregion 33D which are arranged in the transverse direction with respectto the reset gate electrode 34 so that the gate length extends in thetransverse direction. When one sharing unit 21 is observed, the resettransistor Tr2 has the reset gate electrode 34 which is divided into onehalf of the reset gate electrode 34 having the source region 33S and theother half of the reset gate electrode 34 having the drain region 33D.In this case, the divided reset gate electrodes 34 are formed so thatthe source region 33S opposes the drain region 33D.

Next, as illustrated in FIG. 30B, the readout wirings 261 to 268 areformed by the first-layer metal wirings M1 so as to extend in thetransverse direction and be connected to the readout gate electrodes 221to 228, respectively. Moreover, connection portions 116, which areconnected to the floating diffusions FD1 and FD2, and connectionportions 117, which are connected to the source region 31S and the drainregion 31D of the amplification transistor Tr3, are formed by thefirst-layer metal wirings M1. Furthermore, a connection portion 118connected to the amplification gate electrode 32 is formed by thefirst-layer metal wirings M1. Furthermore, a connection wiring portion281 is formed by the first-layer metal wirings M1 so as to extend in thelongitudinal direction and be connected to the source region 33S of thereset transistor Tr2. Furthermore, divided reset wiring portions 271,which are connected to the respective reset gate electrodes 34corresponding to adjacent sharing units 21, and divided power supplywiring portions 291, which are connected to the respective drain regions33D, are formed by the first-layer metal wirings M1. The ends of thedivided power supply wiring portions 291 are formed so as to oppose eachother at positions where the source region 33S positioned at the centerin the transverse direction of the sharing unit 21 is sandwiched by theends. Furthermore, a wavy wiring 121 is formed in the transversedirection by the first-layer metal wirings along the amplification gateelectrode 32 of the amplification transistor Tr3 while moving aside fromthe connection portions 117 on the source and drain regions 33S and 33Dand the connection portion 118 connected to the amplification gateelectrode 32. This wavy wiring 121 is used for applying a substratevoltage, namely a predetermined voltage to the semiconductor well regionin which the photodiodes and the pixel transistors are formed. Forexample, when an n-type substrate is used, a voltage of 0 V is appliedto a p-type semiconductor well region in which the photodiodes and thepixel transistors are formed. Although this wiring 121 is the wiring forapplying a voltage of 0 V to the p-type semiconductor well region, inthis example, it is also referred to as a substrate contact wiring.

Next, as illustrated in FIG. 30C, the vertical signal line 35 connectedto the source region 31S of the amplification transistor Tr3 and thepower supply wiring 36 connected to the drain region 31D are formed inthe longitudinal direction by the second-layer metal wirings M2.Moreover, the connection wiring 28 is formed by the second-layer metalwirings M2 so as to be connected via the connection portions 116 and 118to the floating diffusions FD1 and FD2, the amplification gate electrode32, and the connection portion 281 which is connected to the sourceregion 33S of the reset transistor Tr2. Furthermore, a connection wiringportion 292 is formed by the second-layer metal wirings M2 so as toconnect the power supply wiring portions 291 which are connected to thedrain region 33D of the reset transistor Tr2. By the power supply wiringportion 291 formed by the first-layer metal wirings M1 and theconnection wiring portion 292 formed by the second-layer metal wiringsM2, the power supply wiring 29 is formed which is connected to the drainregion 33D of each of the reset transistors Tr2 of the sharing units 21arranged in the horizontal direction. Furthermore, a connection wiringportion 272 is formed in the transverse direction by the second-layermetal wirings M2 so as to connect the reset wiring portions 271 beingconnected to the reset gate electrode 34. By the reset wiring portions271 formed by the first-layer metal wirings M1 and the connection wiringportion 272 formed by the second-layer metal wirings M2, the resetwiring 27 is formed which connects the reset gate electrodes 34 of thesharing units 21 arranged in the horizontal direction. Furthermore,optically dummy wirings 122 are formed by the second-layer metal wiringsM2 on the side of the amplification transistor Tr3 at partial areas ofthe wiring 121 that applies a so-called substrate voltage.

According to the solid-state imaging device 115 of Embodiment 12, thesource region 33S of the reset transistor Tr2 is not disposed near theboundary of the photodiodes PD1 and PD2 but is disposed on an upper sideof the photodiodes PD. Due to this configuration, it is better able todecrease the spacing between the photodiodes PD arranged in thehorizontal direction (transverse direction) without being interrupted bythe source region 33S, than Embodiment 1 illustrated in FIG. 2.Accordingly, it is possible to increase the area of each of thephotodiodes PD and further improve the sensitivity. Moreover, since thereset wiring 27 and the power supply wiring 29 connected to the resettransistor Tr2 are formed so as to extend along the reset gate electrode34, it is possible to decrease the spacing between two sharing units 21being adjacent in the vertical direction. Accordingly, it is possible toincrease the area of each of the photodiodes PD and further improve thesensitivity. In addition to this, the same advantages as those describedin Embodiment 1 can be obtained.

Embodiment 13: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 31, a solid-state imaging device, namely an MOSsolid-state imaging device, according to Embodiment 13 of the presentinvention is illustrated. FIG. 31 illustrates a main part of a layout ofa pixel portion using a two-layer wiring structure.

A solid-state imaging device 130 according to Embodiment 13 has aconfiguration such that the substrate contact wiring 121 and the dummywirings 122 formed thereon are omitted from the configuration of thesolid-state imaging device 115 of Embodiment 12. However, the dummywirings 122 may be formed as illustrated by a chain line in the figure.Since other configurations are the same as those described in Embodiment12, portions corresponding to those in FIG. 29 will be denoted by thesame reference numerals, and description thereof will be omitted.

According to the solid-state imaging device 130 of Embodiment 13, thesame advantages as those of the solid-state imaging device 115 ofEmbodiment 12 can be obtained since the solid-state imaging device 130has the same configuration as that of Embodiment 12 except that thesubstrate contact wiring 121 is omitted.

Embodiment 14: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 32, a solid-state imaging device, namely an MOSsolid-state imaging device, according to Embodiment 13 of the presentinvention is illustrated. FIG. 32 illustrates a main part of a layout ofa pixel portion using a two-layer wiring structure. A solid-stateimaging device 129 according to Embodiment 14 includes dummy wirings 91which are formed by the second-layer metal wirings M2. That is to say,in addition to the configuration of Embodiment 12 illustrated in FIG.29, dummy wirings 122 and 91 are formed between the readout wirings 261and 264, between the readout wirings 265 and 268, on partial areas ofthe substrate contact wiring 121, and under the floating diffusion FD2.Since other configurations are the same as those described in Embodiment12 illustrated in FIG. 29, corresponding portions will be denoted by thesame reference numerals, and description thereof will be omitted.

According to the solid-state imaging device 129 of Embodiment 14, thephotodiodes PD are surrounded, with a good symmetry, by the dummywirings 91, the vertical signal line 35, the power supply wiring 36, andthe connection wiring which are formed by the second-layer metal wiringsM2. Due to this configuration, it is possible to prevent a color mixturedue to diffraction of light. In addition to this, the same advantages asthose described in Embodiment 12 can be obtained.

Embodiment 15: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 33 and FIGS. 34A to 34C, a solid-state imagingdevice, namely an MOS solid-state imaging device, according toEmbodiment 15 of the present invention is illustrated. FIG. 33illustrates a main part of a layout of a pixel portion using a two-layerwiring structure. FIGS. 34A to 34C are exploded planar views forunderstanding the patterns of first-layer wirings and second-layerwirings.

As illustrated in FIG. 33, similar to Embodiment 1, a solid-stateimaging device 120 according to Embodiment 15 includes one sharing unit21 which includes photodiodes PD (PD1 to PD8) of 8 pixels in total (2pixels by 4 pixels, respectively, in horizontal and vertical directions)and ten pixel transistors. Such sharing units 21 are arranged in atwo-dimensional array to form a pixel portion 3. The photodiodes PD1 toPD8, the readout transistors Tr11 to Tr18 forming the pixel transistorsTr2, and the amplification transistor Tr3 have the same configuration asthat of Embodiment 1.

In this embodiment, in particular, the readout wirings 261 to 268, andthe reset wiring 27 and the power supply wiring 29, which are connectedto the reset transistor Tr2, are laid out differently. That is to say,the readout wirings 261 to 268 are laid out using the first andsecond-layer metal wirings M1 and M2 so as to shield a region includingthe readout gate electrodes 221 to 228 and partly form two wirings asviewed in a top plan view thereof. Moreover, the reset wiring 27 and thepower supply wiring 29 which are connected to the reset transistor Tr2are laid out using the first and second-layer metal wirings M1 and M2 soas partly to form one wiring as viewed in a top plan view thereof.

First, as illustrated in FIG. 34A, an array of photodiodes PD1 to PD8corresponding to an arrangement of 2 pixels by 4 pixels, the floatingdiffusions FD1 and FD2, and the readout transistors Tr11 to Tr18 havingthe readout gate electrodes 221 to 228 are formed. Furthermore, thereset transistor Tr2 and the amplification transistor Tr3 are formed.The reset transistor Tr2 has the reset gate electrode 34 and the sourceregion 33S and the drain region 33D which are arranged so that the gatelength extends in the transverse direction. The amplification transistorTr3 includes the amplification gate electrode 32, which extends in thetransverse direction, and the source region 31S and the drain region 31Dwhich are disposed at both ends of the amplification gate electrode 32.These layouts are the same as those of Embodiment 1.

Next, as illustrated in FIG. 34B, by the first-layer metal wirings M1,the readout wiring 262 connected to the readout gate electrode 222 isformed in a straight-line shape in the transverse direction and is bentin an inverted-U shape on the readout gate electrodes 221 and 222.Moreover, by the first-layer metal wirings M1, straight-line shapedwiring portions 261 a and 261 b are formed in the transverse directionto be divided so as to form a part of a readout wiring connected to thereadout gate electrode 221. The wiring portion 261 a is connected to thereadout gate electrode 221 at an inner side of the inverted-U shapedportion of the readout wiring 262 and is formed over both readout gateelectrodes 221 and 222. The wiring portion 261 b is formed above thestraight-line portion of the readout wiring 262 so as to be positionedat both ends in the transverse direction of the sharing unit 21.

The readout wiring 263, which is connected to the readout gate electrode223, and wiring portions 264 a and 264 b, which form a part of thereadout wiring 264, are formed by the first-layer metal wirings M1 to belinearly symmetrical to the layout of the readout wiring 262 and therear-end wall portion 261 a and 261 b.

With the same layout, the readout wiring 266, which is connected to thereadout gate electrode 226, and wiring portions 265 a and 265 b whichform a part of the readout wiring 265 connected to the readout gateelectrode 225 are formed by the first-layer metal wirings M1. Moreover,the readout wiring 267, which is connected to the readout gate electrode227, and wiring portions 268 a and 268 b which form a part of thereadout wiring 268 connected to the readout gate electrode 228 areformed.

Moreover, connection portions 116, which are connected to the floatingdiffusions FD1 and FD2, and connection portions 117, which are connectedto the source region 31S and the drain region 31D of the amplificationtransistor Tr3, are formed by the first-layer metal wirings M1.Furthermore, a connection portion 118 connected to the amplificationgate electrode 32 is formed by the first-layer metal wirings M1.Furthermore, the reset wiring 27 which is connected to the reset gateelectrode 34 of the reset transistor Tr2 is formed by the first-layermetal wirings M1 so as to extend in the transverse direction, and powersupply wiring portions 291 forming a part of the power supply wiring 29are formed at both ends in the transverse direction of the sharing unit21. The power supply wiring portions 291 and the reset wiring 27 areformed in parallel to the reset wiring 27.

Next, as illustrated in FIG. 34C, the vertical signal line 35 connectedto the source region 31S of the amplification transistor Tr3 and thepower supply wiring 36 connected to the drain region 31D are formed inthe longitudinal direction by the second-layer metal wirings M2.Moreover, the connection wiring 28 is formed by the second-layer metalwirings M2 so as to extend in the longitudinal direction and beconnected via the connection portions 116 and 118 to the floatingdiffusions FD1 and FD2, the amplification gate electrode 32, and thesource region 33S of the reset transistor Tr2.

In the first structural portion 23, wiring portions 261 c, which connectthe wiring portions 261 a and 261 b forming a part of the readout wiring261, and wiring portions 263 c, which connect the wiring portions 263 aand 263 b forming a part of the readout wiring 263, are formed by thesecond-layer metal wirings M2. The wiring portions 261 c formed by thesecond-layer metal wirings M2 are formed so as to overlap with bothstraight-line portions which sandwich the bent portion of the readoutwiring 261 formed by the first-layer metal wirings M1 and be bent tocover the readout gate electrode and the spacing between the wirings onthe floating diffusion FD1. The wiring portions 263 c formed by thesecond-layer metal wirings M2 are formed so as to overlap with bothstraight-line portions which sandwich the bent portion of the readoutwiring 264 formed by the first-layer metal wirings M1 and be bent tocover the readout gate electrode and the spacing between the wirings onthe floating diffusion FD1.

In the second structural portion 25, wiring portions 265 c, whichconnect the wiring portions 265 a and 265 b forming a part of thereadout wiring 265, and wiring portions 268 c, which connect the wiringportions 268 a and 268 b forming a part of the readout wiring 268, areformed by the second-layer metal wirings M2. The wiring portions 265 cformed by the second-layer metal wirings M2 are formed so as to overlapwith both straight-line portions which sandwich the bent portion of thereadout wiring 266 formed by the first-layer metal wirings M1 and bebent to cover the readout gate electrode and the spacing between thewirings on the floating diffusion FD2. The wiring portions 268 c formedby the second-layer metal wirings M2 are formed so as to overlap withboth straight-line portions which sandwich the bent portion of thereadout wiring 267 formed by the first-layer metal wirings M1 and bebent to cover the readout gate electrode and the spacing between thewirings on the floating diffusion FD2.

In the reset transistor Tr2, a power supply wiring portion 292 is formedby the second-layer metal wirings M2 so as to connect the power supplywiring portions 291 at both ends of the sharing unit 21 and the drainregion 33D together. The power supply wiring portions 291 and 292 formthe power supply wiring 29. The power supply wiring 292 formed by thesecond-layer metal wirings M2 is formed so as partly to overlap with thestraight-line portion of the reset wiring 27 which is formed by thefirst-layer metal wirings M1 so as to extend in the transversedirection. Furthermore, optically dummy wirings 122 are formed by thesecond-layer metal wirings M2 on the side of the amplificationtransistor Tr3 at partial areas of the wiring 121 that applies aso-called substrate voltage.

According to the solid-state imaging device 120 of Embodiment 15, in thefirst structural portion 23, the readout wirings 262 and 261 overlapeach other and the readout wirings 263 and 264 overlap each other, sothat two main horizontal wiring portions appear in a top plan view.Moreover, in the second structural portion 25, two main horizontalwiring portions appear in a top plan view. Due to this configuration, itis possible to increase the area of each of the photodiodes PD1 to PD4of the pixels and achieve improvement in the sensitivity. Furthermore,by the readout wirings 261 to 268 which are arranged at a spacing ofequal to or smaller than the diffraction limit, regions which have to beshielded from light, namely the readout gate electrodes 221 to 228 andthe floating diffusions FD1 and FD2 can be shielded. Therefore, it isnot necessary to form an additional light shielding film. That is tosay, in a configuration where a floating diffusion FD is surrounded byreadout gate electrodes, when readout wirings are formed so as tooverlap the readout gate electrodes, the readout wirings perform thefunction of a light shielding film. Since a distance of around 0.3 μm ismaintained as a readout gate length between the photodiode PD and thefloating diffusion FD, a proper operation of the readout transistorsTr11 to Tr18 is ensured. In the reset transistor Tr2, since the powersupply wiring 29 and the reset wiring 27 partly overlap each other so asto appear as one wiring as viewed in a top plan view, a simple layout isachieved. In addition to this, the same advantages as those described inEmbodiment 1 can be obtained.

Embodiment 16: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 35, a solid-state imaging device, namely an MOSsolid-state imaging device, according to Embodiment 16 of the presentinvention is illustrated. FIG. 35 illustrates a main part of a layout ofa pixel portion using a two-layer wiring structure. A solid-stateimaging device 123 according to Embodiment 16 has a configuration suchthat the layout of the reset transistor Tr2, the reset wiring 27, andthe power supply wiring 29 in the solid-state imaging device 120according to Embodiment 15 is replaced with the corresponding layoutillustrated in Embodiment 12. Since other configurations are the same asthose described in Embodiments 12 and 15, portions corresponding tothose in FIG. 29, FIGS. 30A to 30C, FIG. 33, and FIGS. 34A to 34C willbe denoted by the same reference numerals, and description thereof willbe omitted.

According to the solid-state imaging device 123 of Embodiment 16, it ispossible to decrease the spacing between the photodiodes PD arranged inthe horizontal direction (transverse direction) while preventing thesource region 33S of the reset transistor Tr2 from interfering with thephotodiodes PD. Accordingly, it is possible to increase the area of eachof the photodiodes PD and further improve the sensitivity. Moreover,since the reset wiring 27 and the power supply wiring 29 connected tothe reset transistor Tr2 are formed so as to extend along the reset gateelectrode 34, it is possible to decrease the spacing between two sharingunits 21 being adjacent in the vertical direction. Accordingly, it ispossible to increase the area of each of the photodiodes PD and furtherimprove the sensitivity.

Furthermore, by the readout wirings 261 to 268, the readout gateelectrodes 221 to 228 and the floating diffusions FD1 and FD2, where itis desired that light is not made incident thereto, can be shielded. Inaddition to this, the same advantages as those described in Embodiment 1can be obtained.

Embodiment 17: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 36 and FIGS. 37A to 37C, a solid-state imagingdevice, namely an MOS solid-state imaging device, according toEmbodiment 17 of the present invention is illustrated. FIG. 36illustrates a main part of a layout of a pixel portion having a selecttransistor, which uses a two-layer wiring structure. FIGS. 37A to 37Care exploded planar views for understanding the patterns of first-layerwirings and second-layer wirings.

As illustrated in FIG. 36, a solid-state imaging device 125 according toEmbodiment 17 includes one sharing unit 21 which includes photodiodes PD(PD1 to PD8) of 8 pixels in total (2 pixels by 4 pixels, respectively,in horizontal and vertical directions) and eleven pixel transistors. Thepixel transistors are composed of eight readout transistors Tr11 toTr18, one reset transistor Tr2, one amplification transistor Tr3, andone select transistor Tr4. The equivalent circuit of this solid-stateimaging device 125 is the same as that described in FIG. 28. Suchsharing units 21 are arranged in a two-dimensional array to form a pixelportion.

In one sharing unit 21, the amplification transistor Tr3 and the selecttransistor Tr4 are disposed between the first structural portion 23 andthe second structural portion 25. The select transistor Tr4 includes asource region 83S, a drain region 83D, and a select gate electrode 84and is connected to the amplification transistor Tr3. The source region83S of the select transistor Tr4 is the same region as the drain region31D of the amplification transistor Tr3.

The vertical signal line 35 is connected to the source region 31S of theamplification transistor Tr3, and the power supply wiring 36 isconnected to the drain region 83D of the select transistor Tr4. Theselect gate electrode 84 of the select transistor Tr4 is connected to aselect wiring 85 which extends in the longitudinal direction. The selectgate electrode 84 of the select transistor Tr4 is connected to thelongitudinal select wiring 85, which is formed by the second-layer metalwirings M2, via a horizontal connection line 85 a which is formed by thefirst-layer metal wirings M1.

Since other configurations in FIG. 36 and FIGS. 37A to 37C are the sameas those described in FIG. 33 and FIGS. 34A to 34C, correspondingportions will be denoted by the same reference numerals, and descriptionthereof will be omitted.

According to the solid-state imaging device 125 of Embodiment 17, thesame advantages as those of the solid-state imaging device of Embodiment15 can be obtained since the solid-state imaging device 125 has the sameconfiguration as that of Embodiment 15 except that the select transistorTr4 is added.

Embodiment 18: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 38 to FIGS. 40A and 40B, a solid-state imagingdevice, namely an MOS solid-state imaging device, according toEmbodiment 18 of the present invention is illustrated. FIG. 38illustrates a main part of a layout of a pixel portion using athree-layer wiring structure. FIGS. 39A and 39B and FIGS. 40A and 40Bare exploded planar views for understanding the patterns of first-layerwirings, second-layer wirings, and third-layer wirings.

Similar to Embodiment 1, as illustrated in FIG. 38, a solid-stateimaging device 111 according to Embodiment 18 includes one sharing unit21 in which photodiodes PD (PD1 to PD8) of 8 pixels in total (2 pixelsby 4 pixels, respectively, in horizontal and vertical directions) andten pixel transistors are arranged. Such sharing units 21 are arrangedin a two-dimensional array to form a pixel portion 3. The photodiodesPD1 to PD8 and the readout transistors Tr11 to Tr18 forming the pixeltransistors have the same configuration as that of Embodiment 1.

In this embodiment, in particular, as illustrated in FIGS. 39A and 39Band FIGS. 40A and 40B, the wirings are formed in a three-layer wiringstructure; that is, the wirings are distributed to first-layer metalwirings M1, second-layer metal wirings M2, and third-layer metal wiringsM3. First, as illustrated in FIG. 39A, one sharing unit 21 is formedincluding an array of photodiodes PD1 to PD8 corresponding to anarrangement of 2 pixels by 4 pixels. That is to say, an array ofphotodiodes PD1 to PD8, the floating diffusions FD1 and FD2, the readouttransistors Tr11 to Tr18 having the readout gate electrodes 221 to 228,the reset transistor Tr2, and the amplification transistor Tr3 areformed. Next, as illustrated in FIG. 39B, four readout wirings 261, 264,265, and 268 are formed by the first-layer metal wirings M1 so as toextend in the transverse direction and be connected to the readout gateelectrodes 221, 224, 225, and 228, respectively.

Next, as illustrated in FIG. 40A, four readout wirings 26 (262, 263,266, and 267) are formed by the second-layer metal wirings M2 so as toextend in the transverse direction and be connected to the readout gateelectrodes 22 (222, 223, 226, and 227), respectively. The readoutwirings 26 (262, 263, 266, and 267) formed by the second-layer metalwirings M2 are formed so as to overlap with the readout wirings 26 (261,264, 265, and 268) formed by the first-layer metal wirings M1,respectively. Therefore, when observed in a top plan view, asillustrated in FIG. 38, two readout wirings 26 are disposed between thefirst-row photodiodes PD and the second-row photodiodes PD and betweenthe third-row photodiodes PD and the fourth-row photodiodes PD,respectively. The spacing between the two readout wirings 26 which aredisposed between the rows is set to a value equal to or smaller than thediffraction limit. Moreover, the reset wiring 27, which is connected tothe reset gate electrode 34 of the reset transistor Tr2, and the powersupply wiring 29, which is connected to the drain region 33S, are formedby the second-layer metal wirings M2 so as to extend in the transversedirection.

Next, as illustrated in FIG. 40B, the connection wiring 28, the verticalsignal line 35, and the power supply wiring 36 which is connected to thedrain region 31D of the amplification transistor are formed by thethird-layer metal wirings M3 so as to extend in the longitudinaldirection. The connection wiring 28 is a wiring that connects thefloating diffusions FD1 and FD2, the amplification gate electrode 32,and the source region 33S of the reset transistor together.

Since other configurations are the same as those described in Embodiment1, portions corresponding to those in FIG. 2 will be denoted by the samereference numerals, and description thereof will be omitted.

In Embodiment 18, a first readout pulse is applied through a terminal t1to the readout wiring 261 which is formed by the first-layer metalwirings M1, whereby the readout transistor Tr11 is turned on, andsignals are read from the photodiode PD1. A second readout pulse isapplied through a terminal t2 to the readout wiring 262 which is formedby the second-layer metal wirings M2, whereby the readout transistorTr12 is turned on, and signals are read from the photodiode PD2. A thirdreadout pulse is applied through a terminal t3 to the readout wiring 263which is formed by the second-layer metal wirings M2, whereby thereadout transistor Tr13 is turned on, and signals are read from thephotodiode PD3. A fourth readout pulse is applied through a terminal t4to the readout wiring 264 which is formed by the first-layer metalwirings M1, whereby the readout transistor Tr14 is turned on, andsignals are read from the photodiode PD4.

A fifth readout pulse is applied through a terminal t5 to the readoutwiring 265 which is formed by the first-layer metal wirings M1, wherebythe readout transistor Tr15 is turned on, and signals are read from thephotodiode PD5. A sixth readout pulse is applied through a terminal t6to the readout wiring 266 which is formed by the second-layer metalwirings M2, whereby the readout transistor Tr16 is turned on, andsignals are read from the photodiode PD6. A seventh readout pulse isapplied through a terminal t7 to the readout wiring 267 which is formedby the second-layer metal wirings M2, whereby the readout transistorTr17 is turned on, and signals are read from the photodiode PD7. Aneighth readout pulse is applied through a terminal t8 to the readoutwiring 268 which is formed by the first-layer metal wirings M1, wherebythe readout transistor Tr18 is turned on, and signals are read from thephotodiode PD8.

According to the solid-state imaging device 111 of Embodiment 18, sincethe wirings are formed to be distributed to the first, second, andthird-layer metal wirings M1, M2, and M3 that form a three-layer wiringstructure, the parasitic capacitance connected to the floatingdiffusions FD1 and FD2 can be decreased. That is to say, since theconnection wiring 28 connected to the floating diffusions FD1 and FD2 isformed by the third-layer metal wirings M3, the spacing between theconnection wiring 28 and the semiconductor substrate can be increased.Therefore, the parasitic capacitance formed between the connectionwiring 28 and the semiconductor substrate can be decreased, and theconversion efficiency can be improved. Furthermore, when observed in atop plan view, since two readout wirings 26 are disposed between therows, the aperture area of each of the photodiodes PD1 to PD8 can beincreased to be larger than that of Embodiment 1. Therefore, it ispossible to improve the sensitivity of the solid-state imaging device111. In addition to this, the same advantages as those described inEmbodiment 1 can be obtained.

Embodiment 19: Exemplary Configuration of Solid-State Imaging Device

With reference to FIGS. 41 to 44, a solid-state imaging device, namelyan MOS solid-state imaging device, according to Embodiment 19 of thepresent invention is illustrated. FIG. 41 illustrates a main part of alayout of a pixel portion using a four-layer wiring structure. FIGS. 42Aand 42B to FIG. 44 are exploded planar views for understanding thepatterns of first-layer wirings, second-layer wirings, third-layerwirings, and fourth-layer wirings.

Similar to Embodiment 1, as illustrated in FIG. 41, a solid-stateimaging device 112 according to Embodiment 19 includes one sharing unit21 in which photodiodes PD (PD1 to PD8) of 8 pixels in total (2 pixelsby 4 pixels, respectively, in horizontal and vertical directions) andten pixel transistors are arranged. Such sharing units 21 are arrangedin a two-dimensional array to form a pixel portion 3. The photodiodesPD1 to PD8 and the readout transistors Tr11 to Tr18 forming the pixeltransistors have the same configuration as that of Embodiment 1.

In this embodiment, in particular, as illustrated in FIGS. 42A and 42Bto FIG. 44, the wirings are formed in a four-layer wiring structure;that is, the wirings are distributed to first-layer metal wirings M1,second-layer metal wirings M2, third-layer metal wirings M3, andfourth-layer metal wirings M4. First, as illustrated in FIG. 42A, anarray of photodiodes PD1 to PD8 corresponding to an arrangement of 2pixels by 4 pixels and the readout transistors Tr11 to Tr18 having thereadout gate electrodes 221 to 228 are formed. Furthermore, the resettransistor Tr2 and the amplification transistor Tr3 are formed, wherebyone sharing unit 21 is obtained.

Next, as illustrated in FIG. 42B, the connection wiring 28, the verticalsignal line 35, and the power supply wiring 36 which is connected to thedrain region 31D of the amplification transistor are formed by thefirst-layer metal wirings M1 so as to extend in the longitudinaldirection. The connection wiring 28 is a wiring that connects thefloating diffusions FD1 and FD2, the amplification gate electrode 32,and the source region 33S of the reset transistor together.

Next, as illustrated in FIG. 43A, the readout wiring 262 for reading thephotodiode PD2, the readout wiring 264 for reading the photodiode PD4,and the readout wiring 268 for reading the photodiode PD8 are formed bythe second-layer metal wirings M2. These readout wirings 262, 264, and268 are formed so as to extend in the transverse direction so that onlyone wiring appears between the rows. The readout wiring 262 is connectedto the readout gate electrode 222. The readout wiring 268 is connectedto the readout gate electrode 228. The readout wiring 264 is formed witha connection portion 264 a which is formed at the center thereof so asto protrude upward in the figure. The reset wiring 27 connected to thereset gate electrode 34 is formed by the second-layer metal wirings M2so as to extend in the transverse direction.

Next, as illustrated in FIG. 43B, the readout wiring 263 for reading thephotodiode PD3, the readout wiring 266 for reading the photodiode PD6,and the readout wiring 267 for reading the photodiode PD7 are formed bythe third-layer metal wirings M3. These readout wirings 263, 266, and267 are formed so as to extend in the transverse direction and overlapwith the readout wirings 262, 264, and 268, which are formed by thesecond-layer metal wirings M2, so that only one wiring appears betweenthe rows. The readout wiring 263 is connected to the readout gateelectrode 223. The readout wiring 267 is connected to the readout gateelectrode 227. The readout wiring 266 is formed with a connectionportion 266 a which is formed at the center thereof so as to protrudedownward in the figure. The power supply wiring 29 connected to thedrain region 33D of the reset transistor Tr2 is formed by thethird-layer metal wirings M3 so as to extend in the transversedirection.

Next, as illustrated in FIG. 44, the readout wiring 261 for reading thephotodiode PD1 and the readout wiring 265 for reading the photodiode PD5are formed by the fourth-layer metal wiring M4. The readout wiring 261is formed so as to extend in the transverse direction and overlap withthe readout wiring 262 which is formed by the second-layer metal wiringsM2 and the readout wiring 263 which is formed by the third-layer metalwirings M3. The readout wiring 261 is connected to the readout gateelectrode 221 of the readout transistor Tr11 via the connection portionsof the third-layer metal wirings M3 and the second-layer metal wiringsM2. Moreover, a substrate contact wiring 50 which is connected to asubstrate contact portion 50 a is formed by the fourth-layer metalwirings M4. The substrate contact wiring 50 is used for applying asubstrate voltage, namely a predetermined voltage to the semiconductorwell region in which the photodiodes and the pixel transistors areformed. For example, when an n-type substrate is used, a voltage of 0 Vis applied to a p-type semiconductor well region in which thephotodiodes and the pixel transistors are formed.

The readout wiring 265 is formed so as to extend in the transversedirection and overlap with the readout wiring 268 which is formed by thesecond-layer metal wirings M2 and the readout wiring 267 which is formedby the third-layer metal wirings M3. The readout wiring 265 is connectedto the readout gate electrode 225 of the readout transistor Tr15 via theconnection portions of the third-layer metal wirings M3 and thesecond-layer metal wirings M2.

Furthermore, a connection line 264B is formed by the fourth-layer metalwirings M4 so as to connect the readout gate electrode 224 of thereadout transistor Tr14 and a connection portion 264 a of the readoutwiring 264 which is formed by the second-layer metal wirings M2. One endof the connection line 264B is connected to the readout gate electrode224 via the connection portions of the third-layer metal wirings M3, thesecond-layer metal wirings M2, and the first-layer metal wirings M1. Theother end of the connection line 264B is connected to the connectionportion 264 a of the readout wiring 264 formed by the second-layer metalwirings M2 via the connection portion of the third-layer metal wiringsM3. The connection line 264B is formed so as to overlap with theconnection wiring 28 which is formed by the first-layer metal wiringsM1. Furthermore, a connection line 266B is formed by the fourth-layermetal wirings M4 so as to connect the readout gate electrode 226 of thereadout transistor Tr16 and a connection portion 266 a of the readoutwiring 266 which is formed by the third-layer metal wirings M3. One endof the connection line 266B is connected to the readout gate electrode226 via the connection portion of the third-layer metal wirings M3, thesecond-layer metal wirings M2, and the first-layer metal wirings M1. Theother end of the connection line 266B is connected to the connectionportion 266 a of the readout wiring 266 formed by the third-layer metalwirings M3. The connection line 266B is formed so as to overlap with theconnection wiring 28 which is formed by the first-layer metal wiringsM1.

In Embodiment 12, when observed in a top plan view, only one readoutwiring is disposed between the rows of the photodiodes PD.

In Embodiment 19, a first readout pulse is applied through a terminal t1to the readout wiring 261 which is formed by the fourth-layer metalwirings M4, whereby the readout transistor Tr11 is turned on, andsignals are read from the photodiode PD1. A second readout pulse isapplied through a terminal t2 to the readout wiring 262 which is formedby the second-layer metal wirings M2, whereby the readout transistorTr12 is turned on, and signals are read from the photodiode PD2. A thirdreadout pulse is applied through a terminal t3 to the readout wiring 263which is formed by the third-layer metal wirings M3, whereby the readouttransistor Tr13 is turned on, and signals are read from the photodiodePD3.

A fourth readout pulse is applied through a terminal t4 to the readoutwiring 264 which is formed by the second-layer metal wirings M2, wherebythe readout transistor Tr14 is turned on via the connection line 264Bwhich is formed by the fourth-layer metal wirings M4, and signals areread from the photodiode PD4. A sixth readout pulse is applied through aterminal t6 to the readout wiring 266 which is formed by the third-layermetal wirings M3, whereby the readout transistor Tr16 is turned on viathe connection line 266B which is formed by the fourth-layer metalwirings M4, and signals are read from the photodiode PD6.

A fifth readout pulse is applied through a terminal t5 to the readoutwiring 265 which is formed by the fourth-layer metal wirings M4, wherebythe readout transistor Tr15 is turned on, and signals are read from thephotodiode PD5. A seventh readout pulse is applied through a terminal t7to the readout wiring 267 which is formed by the third-layer metalwirings M3, whereby the readout transistor Tr17 is turned on, andsignals are read from the photodiode PD7. An eighth readout pulse isapplied through a terminal t8 to the readout wiring 268 which is formedby the second-layer metal wirings M2, whereby the readout transistorTr18 is turned on, and signals are read from the photodiode PD8.

Although the order of reading the pixel signals is changed, the pixelsignals can be rearranged by a post-processing circuit so that the pixelsignals can be read out in units of rows.

According to the solid-state imaging device 112 of Embodiment 19, sinceonly one readout wiring 26 is disposed between the rows as viewed in atop plan view thereof, the aperture area of each of the photodiodes PD1to PD8 can be increased to be larger than that of Embodiment 1.Moreover, since the wirings are formed in a four-layer wiring structure,the connection lines 264B and 266B which are formed by the fourth-layermetal wirings M4 and are positioned farthest from the connection wiring28 are formed on the connection wiring 28 which is formed by thefirst-layer metal wirings M1 and is connected to the floating diffusionFD1 and FD2. Therefore, the parasitic capacitance formed between theconnection wiring 28 and the connection lines 264B and 266B can bedecreased, and the conversion efficiency can be improved. Therefore, itis possible to improve the sensitivity of the solid-state imaging device112. In addition to this, the same advantages as those described inEmbodiment 1 can be obtained.

Embodiment 20: Exemplary Configuration of Solid-State Imaging Device

With reference to FIG. 45 to FIGS. 47C and 47D, a solid-state imagingdevice, namely an MOS solid-state imaging device, according toEmbodiment 20 of the present invention is illustrated. FIG. 45illustrates a main part of a layout of a pixel portion using afour-layer wiring structure. FIGS. 46A and 46B and FIGS. 47C and 47D areexploded planar views for understanding the patterns of first-layerwirings, second-layer wirings, third-layer wirings, and fourth-layerwirings.

As illustrated in FIG. 45, a solid-state imaging device 127 according toEmbodiment 20 includes one sharing unit 81 which includes photodiodes PD(PD1 to PD8) of 8 pixels in total (2 pixels by 4 pixels, respectively,in horizontal and vertical directions) and eleven pixel transistors. Thepixel transistors are composed of eight readout transistors Tr11 toTr18, one reset transistor Tr2, one amplification transistor Tr3, andone select transistor Tr4. The equivalent circuit of this solid-stateimaging device 125 is the same as that described in FIG. 33. Suchsharing units 81 are arranged in a two-dimensional array to form a pixelportion.

In one sharing unit 81, the amplification transistor Tr3 and the selecttransistor Tr4 are disposed between the first structural portion 23 andthe second structural portion 25. The select transistor Tr4 includes asource region 83S, a drain region 83D, and a select gate electrode 84and is connected to the amplification transistor Tr3. The source region83S of the select transistor Tr4 is the same region as the drain region31D of the amplification transistor Tr3.

As illustrated in FIGS. 46A and 46B and FIGS. 47C and 47D, thesolid-state imaging device according to this embodiment has the sameconfiguration as that of Embodiment 12 except for the select transistorTr4.

First, as illustrated in FIG. 46A, an array of photodiodes PD1 to PD8corresponding to an arrangement of 2 pixels by 4 pixels, the readouttransistors Tr11 to Tr18 having the readout gate electrodes 221 to 228,and the reset transistor Tr2 are formed. Furthermore, the amplificationtransistor Tr3 and the select transistor Tr4 are formed, whereby onesharing unit 21 is obtained. Moreover, a connection wiring 35 is formedby the first-layer metal wirings M1 so as to connect the floatingdiffusions FD1 and FD2, the amplification gate electrode 32, and thesource region 33S of the reset transistor together.

Furthermore, the wirings formed by the first-layer metal wirings M1 areformed. Specifically, the vertical signal line 35 which is connected tothe source region 31S of the amplification transistor Tr3 and the powersupply wiring 36 which is connected to the drain region 83D of theselect transistor Tr4 are formed so as to extend in the longitudinaldirection. Moreover, the select wiring 85 is formed in the longitudinaldirection in parallel to the power supply wiring 36. At the same time,connection portions 131 connected to the readout gate electrodes 221 to228, a connection portion 132 connected to the reset gate electrode 34,a connection portion 133 connected to the select gate electrode 84, anda connection portion 134 for substrate contact are formed by thefirst-layer metal wirings M1.

Next, as illustrated in FIG. 46B, the wirings formed by the second-layermetal wirings M2 are formed. Specifically, the reset wiring 27 is formedso as to be connected to the reset gate electrode 34 via the connectionportion 132. Moreover, the connection line 85 a is formed in thetransverse direction so as to be connected to the select gate electrode84 and the select wiring 85 via the connection portion 133. Theconnection line 85 a is formed so as to cover the entire width of onesharing unit 21. Furthermore, the readout wiring 268 which is connectedto the readout gate electrode 222 via the connection portion 131 and thereadout wiring 268 which is connected to the readout gate electrode 228via the connection portion 131 are formed in the transverse direction.The readout wiring 262 is formed between pixels which are adjacent toeach other in the longitudinal direction of the first structural portion23. The readout wiring 268 is formed between pixels which are adjacentto each other in the longitudinal direction of the second structuralportion 25.

Next, as illustrated in FIG. 47C, the wirings formed by the third-layermetal wirings M3 are formed. Specifically, the power supply wiring 29which is connected to the drain region 33D of the reset transistor Tr2via the connection portion 131 of the first-layer metal wirings M1 andthe connection portion (not illustrated) of the second-layer metalwirings M2 is formed so as to overlap with the reset wiring 27.Moreover, the readout wiring 263 which is connected to the readout gateelectrode 223 via the connection portion 131 of the first-layer metalwirings M1 and the connection portion (not illustrated) of thesecond-layer metal wirings M2 is formed so as to overlap with thereadout wiring 262. Furthermore, the readout wiring 267 which isconnected to the readout gate electrode 227 via the connection portion131 of the first-layer metal wirings M1 and the connection portion (notillustrated) of the second-layer metal wirings M2 is formed so as tooverlap with the readout wiring 268. Furthermore, the readout wiring 266which is connected to the readout gate electrode 226 in a subsequentstep and partly extends between the photodiodes PD5 and PD6 is formed soas to overlap with the connection line 85 a on the amplificationtransistor Tr3.

Next, as illustrated in FIG. 47D, the wirings formed by the fourth-layermetal wirings M4 are formed. Specifically, the readout wiring 261 whichis connected to the readout gate electrode 221 via the connectionportion 131 of the first-layer metal wirings M1 and the connectionportions (not illustrated) of the second and third-layer metal wiringsM2 and M3 is formed so as to overlap with the readout wiring 263.Moreover, the readout wiring 265 which is connected to the readout gateelectrode 225 via the connection portion 131 of the first-layer metalwirings M1 and the connection portions (not illustrated) of the secondand third-layer metal wirings M2 and M3 is formed so as to overlap withthe readout wiring 268. Furthermore, the connection line 266 a whichconnects the readout gate electrode 226 and the readout wiring 266formed by the third-layer metal wirings M3 together via the connectionportion 131 of the first-layer metal wirings M1 and the connectionportions (not illustrated) of the second and third-layer metal wiringsM2 and M3 is formed so as to overlap with the connection wiring 28.Furthermore, the readout wiring 264 which is connected to the readoutgate electrode 224 via the connection portion 131 of the first-layermetal wirings M1 and the connection portions (not illustrated) of thesecond and third-layer metal wirings M2 and M3 is formed so as tooverlap with the readout wiring 266 and the connection wiring 28.

In addition, the substrate contact wiring 50 is formed via theconnection portion 131 of the first-layer metal wirings M1 and theconnection portions (not illustrated) of the second and third-layermetal wirings M2 and M3. Moreover, a dummy wiring 89 that overlaps withthe connection wiring 28 between the floating diffusion FD1 and thesource region 33S of the reset transistor Tr2 and a dummy wiring 90 thatoverlaps with the power supply wiring 29 on the reset transistor Tr2 areformed from the consideration of wiring balance.

In Embodiment 20, a first readout pulse is applied through a terminal t1to the readout wiring 261 which is formed by the fourth-layer metalwirings M4, whereby the readout transistor Tr11 is turned on, andsignals are read from the photodiode PD1. A second readout pulse isapplied through a terminal t2 to the readout wiring 262 which is formedby the second-layer metal wirings M2, whereby the readout transistorTr12 is turned on, and signals are read from the photodiode PD2. A thirdreadout pulse is applied through a terminal t3 to the readout wiring 263which is formed by the third-layer metal wirings M3, whereby the readouttransistor Tr13 is turned on, and signals are read from the photodiodePD3.

A fourth readout pulse is applied through a terminal t4 to the readoutwiring 264 which is formed by the fourth-layer metal wirings M4, wherebythe readout transistor Tr14 is turned on, and signals are read from thephotodiode PD4. A sixth readout pulse is applied through a terminal t6to the readout wiring 266 which is formed by the third-layer metalwirings M3, whereby the readout transistor Tr16 is turned on via theconnection line 266 a which is formed by the fourth-layer metal wiringsM4, and signals are read from the photodiode PD6.

A fifth readout pulse is applied through a terminal t5 to the readoutwiring 265 which is formed by the fourth-layer metal wirings M4, wherebythe readout transistor Tr15 is turned on, and signals are read from thephotodiode PD5. A seventh readout pulse is applied through a terminal t7to the readout wiring 267 which is formed by the third-layer metalwirings M3, whereby the readout transistor Tr17 is turned on, andsignals are read from the photodiode PD7. An eighth readout pulse isapplied through a terminal t8 to the readout wiring 268 which is formedby the second-layer metal wirings M2, whereby the readout transistorTr18 is turned on, and signals are read from the photodiode PD8.

Although the order of reading the pixel signals is changed, the pixelsignals can be rearranged by a post-processing circuit so that the pixelsignals can be read out in units of rows.

According to the solid-state imaging device 127 of Embodiment 20,similar to Embodiment 19 described above, since only one readout wiring26 is disposed between the rows as viewed in a top plan view thereof,the aperture area of each of the photodiodes PD1 to PD8 can be increasedto be larger than that of Embodiment 1. Moreover, since the wirings areformed in a four-layer wiring structure, the connection lines 264B and266B which are formed by the fourth-layer metal wirings M4 and arepositioned farthest from the connection wiring 28 are formed on theconnection wiring 28 which is formed by the first-layer metal wirings M1and is connected to the floating diffusion FD1 and FD2. Therefore, theparasitic capacitance formed between the connection wiring 28 and theconnection lines 264B and 266B can be decreased, and the conversionefficiency can be improved. Therefore, it is possible to improve thesensitivity of the solid-state imaging device 127.

Moreover, the dummy wirings 89 and 90 are formed so as to surround eachof the photodiodes PD1 to PD8 in a C shape together with the readoutwirings 261, 264, 266 a, and 225. Due to this configuration, thephotodiodes PD1 to PD8 are surrounded by the metal wirings on the samelayer with a good symmetry, and thus a color mixture due to diffractionof light can be prevented. In addition to this, the same advantages asthose described in Embodiment 1 can be obtained.

The above-described solid-state imaging device having a configuration inwhich one sharing unit 21 is composed of the photodiodes PD (PD1 to PD8)of 8 pixels in total (2 pixels by 4 pixels, respectively, in horizontaland vertical directions) and ten pixel transistors has a longitudinalwiring layout as illustrated in FIG. 48. That is to say, the solid-stateimaging device of the embodiment of the present invention has a layoutin which one longitudinal connection wiring 28 is disposed at the centerof the array of photodiodes PD of eight pixels, and two wirings, i.e.,the vertical signal line 35 and the power supply wiring 36, are disposedbetween the adjacent sharing units 21. Such a wiring layout is verysimple.

Modification of Amplification Transistor

With reference to FIGS. 51 to 57, modified examples of the amplificationtransistor Tr3 which is disposed between the first structural portion 23and the second structural portion 24 are illustrated.

The amplification transistor Tr3 illustrated in FIG. 51 has aconfiguration such that an active region 87 extending from the sourceregion 31S to the drain region 31D via a channel region is bent at aright angle, and the amplification gate electrode 32 is formed on aregion including the bent portion. The active region 87 that is bent ata right angle into an L shape has one part thereof which is formed inthe transverse direction between the rows of photodiodes PD and theother part thereof which is formed in the longitudinal direction betweenthe columns of photodiodes PD. The amplification gate electrode 32 isformed in a straight-line shape in the transverse direction between therows of photodiodes PD.

According to the amplification transistor Tr3 illustrated in FIG. 51,since the active region 87 is formed to be bent at a right angle, thegate length Lg increases, and thus the 1/f noise can be suppressed.

The amplification transistor Tr3 illustrated in FIG. 52 has aconfiguration such that an active region 87 extending from the sourceregion 31S to the drain region 31D via a channel region is bent at aright angle, and the amplification gate electrode 32 is bent at a rightangle so as to follow the bent active region 87. The active region 87that is bent at a right angle into an L shape has one part thereof whichis formed in the transverse direction between the rows of photodiodes PDand the other part thereof which is formed in the longitudinal directionbetween the columns of photodiodes PD. Similarly, the amplification gateelectrode 32 that is bent at a right angle into an L shape has one partthereof which is formed in the transverse direction between the rows ofphotodiodes PD and the other part thereof which is formed in thelongitudinal direction between the columns of photodiodes PD.

According to the amplification transistor Tr3 illustrated in FIG. 52,since the active region 87 is formed to be bent at a right angle, andthe amplification gate electrode 32 is formed to be bent at a rightangle so as to follow the active region 87, the gate length Lg increasesfurther, and thus the 1/f noise can be suppressed. Here, as an elementseparation region around the active region 87, as described above, byusing a flat element separation region which is formed in an impuritydiffusion region (e.g., a p-type semiconductor region) and a flatinsulating film is formed on a surface thereof, it is possible toprevent concentration of stress on the L-shaped bent portion of theactive region 87. That is to say, generation of noise due toconcentrated stress can be suppressed. However, when the elementseparation region has an STI structure, there is a concern that stressmay be concentrated on the L-shaped bent portion of the active region87, and thus noise may be generated due to the concentrated stress.

The amplification transistor Tr3 illustrated in FIG. 53 has aconfiguration such that an active region 87 including the source region31S, the channel region, and the drain region 31D is formed in a crossshape, and the amplification gate electrode 32 is formed on the verticalportion of the channel region 87.

According to the amplification transistor Tr3 illustrated in FIG. 53,the gate width Wg increases, and thus the 1/f noise can be suppressed.

The amplification transistor Tr3 illustrated in FIG. 54 has aconfiguration such that an active region 87 including the source region31S, the channel region, and the drain region 31D is in a straight-lineship in the longitudinal direction to be positioned between the columnsof photodiodes PD. The amplification gate electrode 32 is formed in astraight-line shape in the transverse direction to be positioned betweenthe rows of photodiodes PD with the source region 31S and the drainregion 31D being extended from the active region 87.

The amplification transistor Tr3 illustrated in FIG. 55 has aconfiguration such that an active region 87 which is positioned betweenthe rows of photodiodes PD and includes the source region 31S, thechannel region, and the drain region 31D is formed with a length of twopixel pitches, and the amplification gate electrode 32 is formed with alength smaller than two pixel pitches. Although the length in the gatelength direction of the amplification gate electrode 32 is preferablyset to be equal to or larger than one pixel pitch, it may be formed tobe smaller than one pixel pitch.

The amplification transistor Tr3 illustrated in FIG. 56 has aconfiguration such that an active region 87 which is positioned betweenthe rows of photodiodes PD and includes the source region 31S, thechannel region, and the drain region 31D is formed with a length smallerthan two pixel pitches, and the amplification gate electrode 32 isformed on the channel region 87. The vertical signal line 35 and thepower supply wiring 36 which are connected to the source region 31S andthe drain region 31D, respectively, are formed so as partly to extendbetween the rows of photodiodes PD.

The amplification transistor Tr3 illustrated in FIG. 57 has aconfiguration such that an active region 87 which includes the sourceregion 31S, the channel region, and the drain region 31D is formed inthe transverse direction with a length of two pixel pitches, and theamplification gate electrode 32 is formed in the longitudinal directionto be vertical to the active region 87. The active region 87 is formedbetween the rows of photodiodes PD, and the amplification gate electrode32 is formed between the columns of photodiodes PD.

These layouts of the amplification transistors Tr3 illustrated in FIGS.51 to 57 can be applied to the solid-state imaging device according tothe above-described embodiments of the present invention. Since theamplification transistor Tr3 is formed at the central portion of onesharing unit, the degree of freedom of the layout of the amplificationtransistor Tr3 can be increased as illustrated in FIG. 2 and FIGS. 51 to57.

Modification of Reset Transistor

With reference to FIGS. 58 and 59, modified examples of the resettransistor Tr3 are illustrated. The reset transistor Tr2 illustrated inFIG. 58 has a configuration such that an active region 88 including thesource region 33S, the channel region, and the drain region 33D isformed in the longitudinal direction, and the reset gate electrode 34 isformed in the transverse direction with a length of two pixel pitches tobe vertical to the active region 88.

According to the reset transistor Tr2 illustrated in FIG. 58, the resetgate electrode 34 is formed with a length of two pixel pitches. Thereset transistor Tr2 can be well balanced with the amplificationtransistor Tr3 when it is combined with the amplification transistor Tr3having the amplification gate electrode 32 with a length of two pixelpitches.

The reset transistor Tr2 illustrated in FIG. 59 has a configuration suchthat an active region 88 is formed in a cross shape having the channelregion extending in the transverse direction and the source region 33Sand the drain region 33D extending in the longitudinal direction, andthe reset gate electrode 34 is formed in the transverse direction with alength of two pixel pitches.

According to the reset transistor Tr2 illustrated in FIG. 59, it ispossible to increase the channel width Wg. Moreover, since the resetgate electrode 34 is formed with a length of two pixel pitches, it canbe well balanced with the amplification transistor Tr3 when it iscombined with the amplification transistor Tr3 having the amplificationgate electrode 32 with a length of two pixel pitches.

These layouts of the reset transistors Tr2 illustrated in FIGS. 58 and59 can be applied to the solid-state imaging device according to theabove-described embodiments of the present invention. Since the resettransistor Tr2 is formed at the upper central portion of one sharingunit, the degree of freedom of the layout of the reset transistor Tr2can be increased as illustrated in FIG. 2, FIG. 31, and FIGS. 58 and 59.

Although not illustrated in the figure, the above-describedcharacteristic configurations of each embodiment can be combined witheach other to form a solid-state imaging device.

In the examples above, the amplification transistor Tr3 is disposed atthe center of the sharing unit 21, and the reset transistor Tr2 isdisposed on the upper portion of the sharing unit 21. However, thetransistors Tr2 and Tr3 may be disposed at reverse positions; that is,the reset transistor Tr2 may be disposed at the center of the sharingunit 21, and the amplification transistor Tr3 may be disposed on theupper portion of the sharing unit 21. However, the configuration inwhich the amplification transistor Tr3 is disposed at the center of thesharing unit 21, and the reset transistor Tr2 is disposed on the upperportion thereof is advantageous because the connection wiring does notintersect the readout wirings, and accordingly, the floating capacitanceassociated with the floating diffusions can be reduced.

In the examples above, one sharing unit includes an array of photodiodesof 8 pixels in total with 2 pixels by 4 pixels, respectively, inhorizontal and vertical directions. However, one sharing unit mayinclude an array of photodiodes of 2 pixels by 4n pixels (n is apositive integer), respectively, in horizontal and vertical directions,such as, for example, an array of photodiodes of 12 pixels in total with2 pixels by 6 pixels, and an array of photodiodes of 16 pixels in totalwith 2 pixels by 8 pixels.

Embodiment 21: Exemplary Configuration of Solid-State Imaging Device

A solid-state imaging device according to the embodiment of the presentinvention can be applied to electronic apparatuses such as cameras andcamcorders equipped with a solid-state imaging device, or otherapparatuses equipped with a solid-state imaging device. In particular,since pixels can be miniaturized, a camera equipped with a smallsolid-state imaging device can be manufactured.

With reference to FIG. 60, an embodiment of a camera is illustrated asan example of an electronic apparatus according to the presentinvention. A camera 91 according to the present embodiment includes anoptical system (optical lens) 92, a solid-state imaging device 93, and asignal processing circuit 94. The solid-state imaging device 93 is asolid-state imaging device according to any one of the above-describedembodiments. The optical system 92 causes an image light (incidentlight) from a subject to be focused on an imaging surface of thesolid-state imaging device 93. In this way, signal charges areaccumulated for a predetermined period in photodiodes which arephotoelectric conversion units of the solid-state imaging device 93. Thesignal processing circuit 94 performs various signal processing on theoutput signals from the solid-state imaging device 93 and outputsprocessed signals. The camera 91 of the present embodiment may take theform of a camera module in which the optical system 92, the solid-stateimaging device 93, and the signal processing circuit 94 are integrated.

In the present invention, the configuration of the camera illustrated inFIG. 60 or camera which is represented by mobile phones, for example,and equipped with a camera module may be implemented as a so-calledimaging function module that is a module with imaging capabilities inwhich the optical system 92, the solid-state imaging device 93, and thesignal processing circuit 94 are integrated. The present invention maybe applied to an electronic apparatus which is equipped with such animaging function module.

According to the electronic apparatus of the present embodiment, evenwhen pixels are miniaturized to realize higher definition, and thus asolid-state imaging device is further miniaturized, since thesensitivity of the solid-state imaging device can be improved, it ispossible to provide a high-quality electronic apparatus capable ofproviding higher image quality and higher resolution.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. An imaging device, comprising: a first unitincluding a first set of four photoelectric conversion regions, a firstset of four transfer transistors, and a first floating diffusion; asecond unit including a second set of four photoelectric conversionregions, a second set of transfer transistors, and a second floatingdiffusion, wherein the first floating diffusion and the second floatingdiffusion are electrically connected; an amplification transistor sharedby the first floating diffusion and the second floating diffusion andcoupled to a select transistor; wherein each transfer transistor in thefirst set of four transfer transistors is coupled to a respectivephotoelectric conversion region in the first set of four photoelectricconversion regions, wherein each transfer transistor in the second setof four transfer transistors is coupled to a respective photoelectricconversion region in the second set of four photoelectric conversionregions, wherein the transfer transistors in the first set of fourtransfer transistors are coupled to the first floating diffusion andarranged between the first floating diffusion and the first set of fourphotoelectric conversion regions in a plan view, and wherein thetransfer transistors in the second set of four transfer transistors arecoupled to the second floating diffusion and arranged between the secondfloating diffusion and the second set of four photoelectric conversionregions in the plan view.
 2. The imaging device according to claim 1,further comprising: a substrate including a first side receiving a lightincidence and a second side opposite to the first side; a plurality ofwiring layers disposed over the first side of the substrate, wherein theplurality of wiring layers includes at least four layers being arrangedsequentially with a first layer closest to the first side of thesubstrate.
 3. The imaging device according to claim 2, wherein the firstunit and the second unit are arranged along a first direction, andwherein a part of a connection wiring between the first floatingdiffusion and the second floating diffusion extends along the firstdirection.
 4. The imaging device according to claim 3, furthercomprising: a select transistor coupled to the amplification transistor;and a select wiring coupled to a gate electrode of the selecttransistor, wherein the select wiring extends along the first direction.5. The imaging device according to claim 4, wherein each gate electrodeof the first set of four transfer transistors is substantiallytriangular or trapezoidal in shape, and wherein each gate electrode ofthe second set of four transfer transistors is substantially triangularor trapezoidal in shape.
 6. The imaging device according to claim 5,further comprising: a reset transistor having a source region and adrain region; and a first power supply wiring coupled to the drain ofthe reset transistor, wherein the source region of the reset transistoris coupled to the first floating diffusion and the second floatingdiffusion via the connection wiring, and wherein the first power supplywiring extends along a second direction different from the firstdirection.
 7. The imaging device according to claim 6, wherein aconnection wiring is coupled to the first floating diffusion, the secondfloating diffusion, a gate of the amplification transistor, and thesource region of the reset transistor.
 8. The imaging device accordingto claim 7, further comprising: a second power supply wiring coupled toa drain region of the amplification transistor, wherein the second powersupply wiring extends along the first direction.
 9. The imaging deviceaccording to claim 8, wherein the first power supply wiring is formed inone layer of the plurality of wiring layers, and wherein the secondpower supply wiring is formed in another layer of the plurality ofwiring layers.
 10. The imaging device according to claim 9, wherein eachof the transfer transistors in the first set of four transfertransistors is arranged at a corner of the respective photoelectricconversion region in the first set of four photoelectric conversionregions to which the transfer transistor is coupled, and wherein each ofthe transfer transistors in the second set of four transfer transistorsis arranged at a corner of the respective photoelectric conversionregion in the second set of four photoelectric conversion regions towhich the transfer transistor is coupled.
 11. An imaging device,comprising: a first unit including a first set of four transfertransistors and a first floating diffusion; a second unit including asecond set of four transfer transistors and a second floating diffusion,wherein the first floating diffusion and the second floating diffusionare electrically connected; an amplification transistor shared by thefirst floating diffusion and the second floating diffusion and coupledto a select transistor; wherein the transfer transistors in the firstset of four transfer transistors are coupled to the first floatingdiffusion and arranged between the first floating diffusion and thefirst set of four photoelectric conversion regions in a plan view, andwherein the transfer transistors in the second set of four transfertransistors are coupled to the second floating diffusion and arrangedbetween the second floating diffusion and the second set of fourphotoelectric conversion regions in the plan view.
 12. The imagingdevice according to claim 11, further comprising: a substrate includinga first side receiving a light incidence and a second side opposite tothe first side; a plurality of wiring layers disposed over the firstside of the substrate, wherein the plurality of wiring layers includesat least four layer being arranged sequentially with a first layerclosest to the first side of the substrate.
 13. The imaging deviceaccording to claim 12, wherein the first unit and the second unit arearranged along a first direction, and wherein a part of a connectionwiring between the first floating diffusion and the second floatingdiffusion extends along the first direction.
 14. The imaging deviceaccording to claim 13, further comprising: a select transistor coupledto the amplification transistor; and a select wiring coupled to a gateelectrode of the select transistor, wherein the select wiring extendsalong the first direction.
 15. The imaging device according to claim 14,wherein each gate electrode of the first set of four transfertransistors is substantially triangular or trapezoidal in shape, andwherein each gate electrode of the second set of four transfertransistors is substantially triangular or trapezoidal in shape.
 16. Theimaging device according to claim 15, further comprising: a resettransistor having a source region and a drain region; and a first powersupply wiring coupled to the drain of the reset transistor, wherein thesource region of the reset transistor is coupled to the first floatingdiffusion and the second floating diffusion via the connection wiring,and wherein the first power supply wiring extends along a seconddirection different from the first direction.
 17. The imaging deviceaccording to claim 16, wherein a connection wiring is coupled to thefirst floating diffusion, the second floating diffusion, a gate of theamplification transistor, and the source region of the reset transistor.18. The imaging device according to claim 17, further comprising: asecond power supply wiring coupled to a drain region of theamplification transistor, wherein the second power supply wiring extendsalong the first direction.
 19. An electronic apparatus comprising: theimaging device according to claim
 1. 20. An electronic apparatuscomprising: the imaging device according to claim 11.